I made a start over the weekend.
Got some offcuts of walnut, so re sawed them and planed down to 12mm thickness, glued together some oak and walnut to form the top, and planed that down to 6mm.
Grooves cut 6mm deep, and 6mm from the top and bottom and mitres cut with tablesaw. Base is 12mm birch ply with a 6mm rebate, so the bottom of the base panel will sit flat with the bottom of the sides and I don't loose too much internal space.
Quick test fit to check all comes together - the lid is 1mm smaller than the grooves - took apart then routed a small chamfer on the inside edge of what will be the lid as wouldn't be able to do that when glued up, will apply chamfer to the outer part of the lid and base later
Cut some grooves for some oak splines to go in, and got them glued up
Then cut down the splines, gave it all a good sanding, and then applied 1 coat of OSMO PolyX Satin. Mainly to check the finish applied ok, past few things I have done I have had so much glue spread by fingers etc its hard to spot till you apply finish and then see the contrast!
Will let that all dry up, and then next step is to cut the lid off - I planned to do this 30mm down from the top edge, and made allowances for this with the splines so they will be dead central once the 3mm for the saw blade is taken into account.
Im looking for hinges now, I recon those smart ones that sit in either end of the sides will be nice, and I think I may cut some oak and leave it slightly protruding at the front (chisel out in the centre of the lid as if putting in a hinge) to act like a lift/flap, and secure the lid with magnets.
I plan to make some insides and may even go all out and follow the guide on lining a box and get the pig skin to do it - may take a while though!!!