Most vises, at least bench mounted ones, have an anvil block built in.
Attachment 324445
You can use that as your block.
Or another cheap easy way is to get a short piece of 90° angle bracket in steel and drill holes in the corners then screw it to a block of wood like a 2X4.
Attachment 324446
You can put your dimples in either of these and a hole for rod. Oh yeah, I got the idea for the pin sized hole from a video I saw from the factory of I think it was Thiers Issard. Whichever one it was it was a french factory and that's how they did it so I figured nthat was good enough for me.