I wish to thank this thread for the inspiration to build a chuck box, my execution may not be anywhere close to what some of you have, but it does work, and wow its exactly what I was looking for after weeks of searching for some kind of solution.
My outside dimensions were fixed by where/how I wanted it to fit -
Bottom draw holds everything for a cup of tea/coffee while out (stove/kettle/2 cups/tea/coffee/sugar/spoons/spare gas)
Top draw holds everything for a bacon sandwich (our meal of choice before walking/cycling) tongs/bread knife/2 plates/Frying pan/space for bread and bacon if I don't use the cooler but most importantly Ketchup for the Mrs haha.
The very top gives me a small amount of space with a removable lid, I just keep a wind break for the stove and maps in here.
For the accessible side I have a space to store the milk if not using the cooler
Everything inside was sized to fit my kit, the lid is held down with the strap that holds it in place, the bottom draw is kept closed in the same way. I made the paracord handles and rope fair leads keep the straps in alignment. The wood is designed for bathrooms with a gloss and matt side, it's around 10mm thick. I used the gloss side where it would require cleaning and where it slides as there are no draw runners, the top draw simply slides on a shelf between the top and bottom.