Making armour stands in minecraft - what's the trick?

if it's the posing you're after next, that's where java and bedrock split. on bedrock you crouch and use it to cycle through the preset poses. on java there's no button for it, arms and poses need commands. place it facing the way you want it to look, it snaps to your direction.

smooth stone slab is nearly always what's wrong. six sticks and one slab builds it, but it has to be the smooth kind: cobble smelted into stone, that stone smelted again into smooth stone, then slabbed. a plain stone slab looks near enough identical in the inventory and the recipe just sits there giving you nothing.