this is missing the plate that would bolt on top (3d printed), and the copper, and the foam, and the bottom of the hole will have arcs supporting each cell (done with a silicone plug shaping resin in the holes), and there will be arcs on the plates as well.
its not waterproof and the cells arent even fully recessed but it would be a solid compression battery. the details on how thick the beam of wood in the center needs to be depends on how big the hole for the screw inserts in it needs to be. as it is drawn here its’ a 5mm beam and 3mm screw holes and everything is roughly accurately sized. this is the general idea.
maybe have foam on both sides or maybe just the outsides or just the inside, its not important.
the copper would cross the center beam connecting cells that way and along the sides. it will also need to have nubs behind it supporting the nubs in the copper and that could be formed no problem at the same time as the cell support arcs.