A fire pit should be built at least 15 feet from any structure and close to a water source. Ideally, you’ll want it on level ground; it’ll make building it much easier and sitting around it more comfortable.
The size of your fire pit will be determined by your metal fire ring. Place the ring and retaining-wall blocks on the ground to figure out the size of the fire pit. Mark the outside of the circle with the edge of a shovel.
Move the retaining wall blocks out of the way and dig inside the marked hole. Make the hole at least 7” deep.
Add a 1” layer of all-purpose sand in the hole and tamp it down flat. You may want to use a level to make sure it's all on the same plain.
Lay the bottom row of blocks inside the hole. Place the outside of the block on the very edge of the sand.
Place the metal ring on the sand inside the base row of blocks.
Lay the pavers or fireplace bricks in the bottom of the fire pit. Cover as much area as possible.
Fill the gaps between the blocks and the pavers with pea gravel.
Stack the outer blocks to your desired height. Stagger the seams of each layer.