These strange blocks can be brought out by pressing Z and the arrow keys, fishing them out of the void and putting them on the edge of the map, where you can "move" them to where desired. Keep in mind you have to put them in situ.
Large chunks of empty space surrounded on one side only is treated as void when testing the level, even if that area is where you can place blocks.
If a portal is in the Void, a glitched portal's inside that resembles a butt will appear. (This only happens at the top and left sides, and will not remain when the level is published.) If the wheel teleports to this, it will be transported to who knows where and burst after a second due to the fact it teleports into the void, outside of the normal safe area.