It can be much more simple, just a piece of plywood screwed securely to a 4x4 post.

Prop bolt hole orientation is a personal preference. All of mine are drilled with two holes lined up on the two propeller blades though many prefer to have two holes about 45 degrees from there so the engine is coming up on compresion with the propeller blades at about the 1:30 and 7:30 clock positions.