Place 6 sticks in the crafting table
Place 1 smooth stone slab in the center bottom slot
Arrange the sticks in a T shape:
Top row: one stick in the center
Middle row: one stick in the left, one stick in the center, one stick in the right
Bottom row: one stick in the center, with the smooth stone slab directly below it
Craft the armor stand
Place the armor stand on the ground
Equip armor by right-clicking or using the interact button on it