heads up for the step after - the ingot isn't enough to upgrade gear on its own any more. you need a netherite upgrade smithing template as well, and those come from bastion chests. diamond item, template and ingot go in the smithing table.
before you use your first template, copy it: seven diamonds, the template and a netherrack makes two. otherwise you're back raiding bastions for every piece.
the ingot part is the quick half - four scrap plus four gold in the grid, no smithing table needed for that step. ancient debris is the slog. around y -16 is where it's densest, and it doesn't burn, so if you clear a tunnel with beds or tnt the lava goes and the debris is left sitting there obvious. smelt it to scrap first, furnace or blast furnace, either works.