Looking for a flat block-like piece to connect to a picatinny rail

Several ways come to mind, you might want to try to get some weaver rings. Remove the top part. What is left you now have the bottoms. They can be recessed into a piece of dimesionally stable wood. Baltic birch 1/2" ply would be my first choice, you have some good looking wood in Hawaii.Koa maybe. A drill bit, scroll saw recess two rings into a 1/2" thick piece. glue another piece to the bottom. Use 5 minute epoxy make it to the width you desire. Dry fit the rings to your rail first. You could also just leave flat and screw the scope rings to a say 1" by 2 .25"by sat 6" #4 screws should work. Just remove the base when not needed for bench rest shooting
 
"Michael"I recently added a BT15 picatinny rail to my Royale 400 to use a bi-pod. Problem is now I can't use it on my benchrest. Can anyone recommend a flat block-like adapter that I can connect to the rail so my rifles sits flush in the benchrest?

Michael, not quite sure what you are after, but I picked this up at Wally World and it has a length of about 6.25 inches and can be easily trimmed to a shorter length if needed. It's soft and comfortable. Red tag sale for $5.
Larry