Began with the supporting sticks which will give the structural rigidity to make that table steady. Just a hazel sapling bout thumb thick, cut into three pieces. The shortest will be somewhat higher where its length will be sufficient. The lowest bar will connect the thinnest leg with the lone one, that was I tried to find the height for.
The problem will be keeping the chisel in the right angle to carve the slot for the stick. Probably will have to drill through first and follow that hole. However I first I'll have to find the place to carve, so will re-string it so the cord will stretch at the center line of the legs.
I picked a 10 mm thick chisel, a 10 mm wide hole will be enough.
Another point of potential failure is the stick's crookedness. It will serve fine, but it's not that easy to make the flat ends parallel.