Shoulder straps, back. I used a mesh fabric with a layer of, drum roll please, grippy, non skid drawer liner beneath it. Yeah, the stuff you put under carpets to prevent them slipping, or in the bottom of a drawer to prevent the cutlery tray from banging around. Perhaps a completely ghetto solution, but it’s perforated, allowing for some breathability while still providing some padding.
Shoulder straps, front. PALS webbing on the lower part to allow for mounting of a phone pouch or the like to.
When I’m done I intend to make another set of shoulder straps, this one out of a plasticized mesh, somewhat similar to the straps on some Deuter packs. Swap them out in summer time for more breathability in really hot weather.