Earlier quoted context omitted.
just need an oven with good temp control. there is this lovely bronze color you can get on stainless.its strangely alot more stable than color you get from heat treating mild steel...but i bet it would rub off if you used it a nontrivial amount
The problem I imagine would be with the corner pieces. You'd need three different temperatures for the three different faces (with stable temperature across each face). I imagine that achieving this might be still technologically possible but almost certainly non-trivial.
The only way I could see of achieving that would be to heat each face very rapidly with something like a high-powered infrared laser, so it can reach oxide-forming temperature before the heat has time to spread. The low thermal conductivity of stainless steel compared to many other metals would actually be rather useful here.