A sled can be made very easily. You can tell machine where you want it to start carving. I have a few I use that are mdf boards with a 3.5" piece glued and screwed to the one end and another 3.5" piece screwed to the other end that almost doubles as a clamp . I place project board tight to glued side and screw the second board tight to the project board. if the project requires rails I screw them down as needed, most of you projects do not require rails. I also get my mdf from furniture or counter tops that are being tossed out. Saw the stuff up in what you need, and I know that there is no love lost on the wood being sacrificed, junk is junk and you can't wreck junk is one rule I run with.