In diagnosing my previous problem, I know that an insufficiently reducing environment will yield copper oxides rather than copper metal. Unfortunately, insufficient heat will yield exactly the same thing, so that doesn't help. However, if the problem is low temperature, then it's going to be a real issue. Too much oxygen, on the other hand, is relatively easy to solve, so I'll start with that.
I took the copper oxides from smelts 1 & 2 and crushed them in a mortar and pestle. This yielded somewhat-fine oxide powder, which I put into the terracotta saucers
Now I plan to get a little extra clay, and seal the saucers together, top and bottom leaving a small hole for a little gaseous expansion, mix in a little charcoal dust to absorb any low-hanging fruit on the oxygen tree, and fire up the forge once again.
Hopefully, these little saucers will be half-filled with circular copper ingots at the end of the process
Wish me luck!