Work on horizontal surfaces. In other words do the sole then turn the box on its side and do the down side, etc. With epoxy you should be able to do two surfaces a day (one morning, one late afternoon). The reason I suggested using prefab for the sides of the well was that you can do all the actual glass work on a horizontal surface and then glue the panels (which will have one finished side requiring no further finishing) to the plywood with epoxy (thicken the epoxy with 403 microfibers and apply it with a notched trowel), or us the adhesive of your choice - 5200, contact cement, etc.. I would lay up the panels with polyester resin because it is much easier to wet fabrics out with it and it sets up much faster than epoxy. It would stink up your garage a bit but only for two days. Poly is also much cheaper then epoxy. Doing it that way saves the difficulty of filling the weave of the epoxy (3 coats minimum with 10 oz glass unless you use thickened epoxy). If you do it in situ you will be sanding a LOT of epoxy.