Minecraft wiki entry for Nether_survival, associated text: After you got the skulls and soul sand needed, and have picked the place to spawn the wither, place 4 soul sand in a T shape, and place 2 skulls on top, but don't place the 3rd one until you are ready to fight. Prepare at least a full set of iron/diamond armor with a piece of gold armor. Bring fire resistance, and a netherite sword/pickaxe. Bring a bow with as many arrows as possible. (You can get arrow from bastions, or you can barter for spectral arrows.)