“Finished” picture (I ain’t movin that dirt today) + progress pics.

Air is fed in through the extension in the stone ring to a vent underneath the (old, shitty, broken) fire grate. The vent is surrounded with loose bricks, so large debris shouldn’t be an issue. The vent is probably 8” off the ground, so ample room for wood/coals/ash to pile around but still beneath it. I can easily fit my shovel in to scoop ash.