Requested of me was a box for two glass goblets, to protect them while they were on the wagons to and from events.
I had a rough sawn plank of sufficient width which I planed smooth. Then cut to size and rebated for the corners. Then they are trimmed up for final fitting with a chisel.
Several extant small coffrets have square feet in the corners. As there was a bit left of the plank I thought that this box too should have them as well. As the remaining piece was 6 13/16 the math for that would be difficult at best. Here then a medieval technique to the rescue! They aren't called dividers for nothing.
Gimlet then for the pilot holes, that the nails don't split the timbers.