I have obsidian and hellstone ore, but I can’t craft it. I have also tried using a hellforge but it didn’t work either. I think I need molten armor to beat the wall of flesh and I need the Phoenix blaster.
All you need 3 hellstone ore, obsidian and a hellforge.
You can use the hellforges down in the underworld, or take one from there to place in your home base. Crafting will work in either location however.