So, dig out the hole, at the bottom, place those light resistor thingys to make the armor stands taller (so you can actaully see them stick out the ground), then place the armor stands with an iron helmet in each corner. IF PLACE WHILE STOOD ON THE CENTER BLOCK (labled as 🔥) ALL ARMOR STANDS SHOULD BE FACING YOU. (Use the X's if needed) ❌️🟫❌️ 🟫🔥🟫 ❌️🟫❌️ Once they are in the corner, use pistons to push it more towards the center (or where the fire is going to be) (use arrows) 🟫⬇️🟫⬇️🟫 ➡️❌️🟫❌️⬅️ 🟫🟫🔥🟫🟫 ➡️❌️🟫❌️⬅️ 🟫⬆️🟫⬆️🟫 and once they are where you want them, place the other armor stands and iron helmets that surrounds the centre block. (Use the X's) 🟫❌️🟫 ❌️🔥❌️ 🟫❌️🟫 Then, use pistons the push dirt down into blocks you have placed the armour stands, leaving only the helmet visible sticking out the tob of the grass. Finally place your nether rack and fire in the center Also key for the emojis incase there was any confusion: ❌️ is to indicate the armour stands, both how to place or move them 🔥 is where the center is and when the fire is meant to go once completed 🟫 is to signify dirt or irrelevant blocks to the current instruction ⬆️⬇️⬅️➡️ all arrows signify a piston, with the direction of the arrow showing the way the piston should be facing Hope this helps ❤