Hick, if you have some basic tools like a tin snips, sharp pointy scribe, straight edge like item, block of wood and wp pliers you can MAKE a box to your own design.
Oh, a hammer and tape measure are useful too.
You will need those tools and a bit of tin to practice on then the one adequate to make your tin.
I am not big on precise but I can and did make lots of tins barely measuring stuff. Six of them are in the shop owned by my current boss. Solid as a brick in the better ones.
If you want a step by step pictorial guide scrape up some old tin and prepare the tools, then say go.
I am prepared now.
Note I did not say press break and Beverely shear which would make it easier but it would be a 5 grand socket tin to tool up.