This blog is not easy to follow. I fullheartedly acknowledge that. If you have become interested in the PLF (PoPLoAFun) system just lately, you probably have trouble to keep up with the details. If you are genuinely interested, I advice you to go back a few months, and start reading from dec 3, 2016. It is worth the effort.
Going back in time
In fact, I'm doing so myself. Just to ingrain the knowledge that has been accumulated along the way. And to look if somebody has fallen of the bandwagon without me noticing it. A musician we can't do without in the future, for instance. This is what I have already found sofar.
The adult human mind is unsuited for chess calculation. This means, that if an adult tries to improve at chess, he must be clever enough to avoid calculation whenever he can. The plf system is designed for exactly that. It determines goals that lie in the future by their characteristics. Only when the goal is determined, we can go back from the future towards the present. From the present on we can calculate towards the future goal again by using our notorious beloved trial and error. Since our goal is already standing firm, the majority of the branches can be pruned beforehand, since they can't possibly lead to the required goal. This way, the adult brain doesn't become overloaded.
Sitting duck
The goal must always be immobile, to at least a certain degree. The goal will be an augmented immobile piece, or the rim of the board (which happens to be an immobile goal for the pawn with "lust zum wander"). Or it can be a square. It must be a sitting duck. Since if it isn't, it will be long fled when we arrive.

Beware of counterattacks 
A square can be a sitting duck too. That might sound obvious to you, since a square seems to be glued to the board, but that is deceiving. The value of a square is determined by the pieces that are in contact with it. When those pieces are immobile, the square is immobile. When the pieces that are in contact with a square move, the value of the square changes. Squares give access to targets. Attacking squares move when the target moves.
We start at the end of the line, which is the sitting duck. The PoPs (Points of Pressure) and the LoAs (Lines of Attack) tell us something about the road from our attackers towards the sitting duck.
Function tells us something about the immobility of the duck and its defenders. Function is, as you might remember, one of the causes of immobility.
I'm not worried about the calculation from the present towards the future. When the goal is clear and the branches are pruned, we are perfectly capable to calculate the line at high speed. The determination of the "viable" sitting duck causes us more trouble.
Looking into the future
Sofar, we have found three ways to look into the future without calculation. Two of the three are musicians that have fallen off the bandwagon during our wild ride towards chess aptitude.
For the demonstration of the three methods to look into the future without calculation, I will make use of the original posts where we discovered the methods. So the positions might look familiar to you. Which is good, since you don't get distracted then by the variations. I will add the link to the original posts, for those of you who want a more thorough look at the positions presented.
First method: ignore obstacles
The first method to look into the future is looking at the geometry of the position. We look at a LoA without being bothered by the fact that there might be obstacles along the road. We trust that calculation will take care of these obstacles later. For now, we only want to determine the sitting duck.Take the following diagram.

Diagram 1. White to move 
We talked extensively about this position
here.
The square c8 is a sitting duck. There are two LoAs converging at c8:
For the time being, we ignore the blockading pieces Bc3, Nc6 and Nd7.
We can only reach c8 in the future. But first we must determine which pieces or squares are the sitting ducks. Since only sitting ducks are worth our efforts. Other targets are too agile.
Only once the sitting ducks are determined, we can go back from the future to the present, and calculate if we can free the LoAs with tempo. If we can, we can be reassured that the duck will still be sitting there when we arrive at it in the future.
Second method: ignore counterplay
Again you start with a sitting duck. See diagram 2

Diagram 2. Black to move 
We talked extensively about this position
here.
The white king is the sitting duck. It is waiting to be mated. White can drum up some counterplay, but that doesn't change the assessment. In the end the sitting duck will be murdered. The only way to avert an immediate demise for white is a sacrifice. Which is just a slower way of loosing in this particular case.
Chess moves come in pairs. That may sound silly, but just think about it for a while. A CCT move triggers an avoidance reaction. A check must be fled from. A capture must be equalized by a counter capture. A threat must be parried. Everything that can be stirred up must be answered first. But in the end the sitting duck will be still there waiting for you. Only if you have a clear picture of the sitting duck, you can come back from the future to the present situation on the board and start calculating forwards in time towards the duck.
Third method: ignore value and defenders
Have a look at the following diagram.

Diagram 3. Black to move 
We talked extensively about this position
here.
c1 is the sitting duck. To be able to see that, you must ignore the defenders of the road towards c1. Only when you have determined the sitting duck, you have a goal in the future. Only
after you determined your goal in the future you can start the calculation of how to harass the defenders of the LoA.
Conclusion
A sitting duck is a stable goal that lies in the future, and doesn't disappear overnight when we need time to get there. We want to determine the sitting ducks without calculation. We can do so by ignoring all kinds of things like obstacles, value of the pieces, defenders and counterplay. That gives us the clearest picture of what we want to accomplish. Until this point, we haven't loaded a burden onto the mind. Only when we have a clear picture of our goal, we can start to calculate. But it is no longer calculation at random in the deplorable tradition of trial and error in the hope for clues. It is calculation aiming at the removal of obstacles, harassing defenders and answering counter attacks until the goal is reached, or until the opponent needs to sacrifice wood in order to prevent you from reaching it.
The theory of looking into the future while ignoring all sorts of things is still in its infancy of course. A lot has to be done to make it more coherent and reusable. But I'm pretty sure that grandmasters prune the tree of analysis in a similar way. Conscious or unconscious.
The positions above might not be the clearest examples. I used them because they triggered the discovery of the methods. Don't worry, we will find better examples in the future.
We saved a few musicians that were fallen off of the bandwagon. We don't know yet who is going to play the piano and who is going to hit the drums though. But what we know for sure is that we are going to need them. In the future.