When more than two snow slabs are placed on top of each other, the player is able to place blocks adjacent to them even if they are standing where the blocks will be placed.
What was expected to happen:
Attempting to place blocks where the player is standing does nothing.
Placing blocks on the side of snow-layer slabs will place the block, even if the player is standing there.
1. This bug can be used to create x-ray machines if transparent blocks are used.
2-4. Works on any size snow-layer.