It seems there is an error in the 3rd example. The rule is, take each figure from left to right and stack each under the previous one. For L and J shapes the top cell is stripped. The L shape dictates that the next shape will be shifted one cell to the right, the J shape tells the next figure to shift to the left. If all examples are right, then the rule is more complicated than that, involving rotating L clockwise, J counterclockwise. Authors claim that it should be solvable by children, then the rule must be simple.

Each of the red shapes in the input are separated by black squares. Starting from the green block, rotate the red shapes 90 degrees and stack them downwards.

Thats the general pattern although my description wasn’t very good.

yeah it's off somehow. rule 1: start at the green dot?

rule 2: glue the left outer piece to the bottom

rule 3: overlap every now and then :D

rule 4: invert some of the pieces every now and then