Not too hard, can be made ambidextrous if you like. We used a double layer of 3/4 inc good plywood, and mounted the legs with Iron pipe flanges from Fleet Farm. The trick is to use hardwood blocks you saw diagonally to achieve a 15 degree angle for the legs. mount to bench, and mount flanges to block. Might want to cap the bottom of the pipe to keep dirt out. 1 & 1/4 inch is good but you can use one inch if you want..
If you have a welder pal you can make leg mounts with flat stock and pipe nipples sawed at the 15 degree angle.
My nest bench is going to be made so I can shoot in a standing position.
