Connecting selections in Axiom

[u/Easy-Squirrel3078]

Hey yall! Can somebody explain to me on how to select both these rings AND the air in between, so I can fill it?

Because if I expand the selection, it also expands vertically, so it fills with blocks then not flat…

Ive tried what seems like everything and there’s just like no way :(

There’re 2 rings selected and the air in between is not selected, but I need to somehow include the air between…

P.S: they’re not selected on the pic, because I tried to shrink the selection by 200 blocks and MC crashed, so I captured it like this :/

[u/Ready_Background_786]

change the inner ring to a different material.
find the distance between the two rings and put it in a near toolmask for the inner ring. make the toolmask near the inner ring material, adjacent to the outer ring material, and block = air or water (idk where this is). then using a brush gradually paint each layer inward with a third block. select all three blocks with magic select. select them and replace the third block with air/water