Mine in the Nether, mainly between Y-level 8 and 22
Use a diamond or netherite pickaxe to mine ancient debris
Look for ancient debris in large exposed areas from lava lakes, caves, and tunnels
Strip mine or branch mine at Y-level 15
Use beds or TNT to blast away netherrack and expose ancient debris
Bring fire resistance potions for lava safety
Smelt ancient debris into netherite scrap
Combine 4 netherite scrap with 4 gold ingots to make 1 netherite ingot
Use a smithing table to upgrade diamond gear to netherite gear