It depends on what you call simple. The simplest is a slab of whatever, no fiddles, (epoxy sealed if oak or mahogany or teak ply) and a solid wood/alum or stainless tubing with a rubber cane tip and the top end with a stub that fits into a 1/4” or so hole. There are spring loaded removable hinges (as my table has) to remove/stow the table, or leave it folded down against the pedestal guard. The hinge halves are mounted to a teak board (1 x 2? 3?) that mounts to the guard with s/s pipe straps.
More complicated are - attached leg or s/s support (mine) that folds and all stays in place if you don’t want to remove it, folding leaves, fiddles, and so on.
There’s no free lunch so if you can define how simple you want (time, materials, ability, man tools,) I can point you to hardware.
Many C-30 Assn forum members have tables - some homemade (mine was from H&L) so why not cross post the question?