To create a custom magic is not the easiest task. You have to get plastic tiles, strings and to find a couple of nice pictures to cut paper tiles from. When you leave those obstacles behind, you face another problem. Two paper squares from different pictures must be placed between two plastic halves. Both sides of the puzzle must be solvable by folding. How to pair and how to orientate paper tiles?
I call my first method "draft tiles way". Main disadvantage of the method is necessity to disassemble the puzzle. You have to replace temporary "draft tiles" with permanent ones. After a few tries I was ready to invent better method. My Fractal Magic was the first one, created without "draft tiles". But I'll try to explain my method using best-known 2x4 magic as an example.
Take paper tiles of the picture, which will stay unsolved in finished magic. Arrange them to get the correct picture.
Turn as a whole to get the reverse side up.
Find a closed path through all tiles. You can step from one tile to another if they are side to side.
Number the tiles with consecutive numbers 1 - 8 along the path.
Prepare paper scheme to write down position and orientation of tiles. Closed path must be found here as well.
Chose any square and write 1 oriented, as you like. You have to select clockwise or counterclockwise direction to proceed. Let's say, you want to place 2 below 1.
Take tiles 1 and 2 from the arranged set and rotate them as a whole to match orientation of 1 in the scheme.
Fold 2 onto 1 and unfold it to the desired place (below 1).
Write down the position and orientation of 2 to the scheme and return tiles to their place. Next tile will be placed to the left fom 2.
Take tiles 2 and 3 as a whole and rotate them to match orientation of 2 in the scheme.
Fold 3 onto 2 and unfold it to the left.
Write down the position and orientation of 3 to the scheme and return tiles to their place. Next tile will be placed over 3.
Take tiles 3 and 4 as a whole and rotate them to match orientation of 3 in the scheme. Fold 4 onto 3 and unfold it up.
Write down the position and orientation of 4 to the scheme and return tiles to their place. Next tile will be placed over 4.
I am sure you can proceed further without my assistance.
Place numbered tiles according the scheme. Put the tiles of other side to form the solved picture.
Put the pairs of paper tiles between the plastic halves and string the Magic.