[ger21]

Assemble the box dry, and apply blue painters tape in the corners, on each board. This will keep the inside clean

Then use small brushes like those show above, and glue up. After the glue dries, peel off the tape inside. You may need to run a chisel into the corners if there are any small beads left over.

 

[ger21]

If the bit is undersize, you need to recut 1 side only of all the joints after offsetting the fence the needed amount.