I have built a compact 1-bit full adder using only torches; the dimensions are 6 wide by 8 tall with a depth of 2. I was able to make this very small thanks to my XOR gate, which is 4x2x4 (I will post it soon; it's also on my Reddit, u/Aggravating_Quiet_85). This full adder is a refined version of the one I have already posted on my Reddit.

I stacked two of my XOR gates on top of each other, and for the carry-out, I used the fact that both XOR gates already have a torch that works when both inputs are on; I simply ORed these signals together.

I have managed to place all the inputs on the base and the carry-out on the side; to put them in a linked row, the mirrored form is needed every other time. This allows the carry-in and carry-out to be on the same side.

This is done in Java Edition.

I have updated this design and posted it.