Kyle Lamb, head instructor of Viking Tactics, has designed a board called a VTAC Board specifically to force shooters into awkward shooting positions. You can get one piece of 4x8' plywood and make two of these boards, and they are a great way to increase the difficulty in your shooting drills.

Per their instructions, "the Viking Tactics Barricade provides the shooter with an extremely functional and transportable training aid that can be built in an afternoon with basic woodworking tools and skills."

Below you can see some of the skills that you can work on using this board: