I have been using a super simple antenna for indoor use that fits in a zip lock bag and just needs masking or duct tape.
I run the wire around the perimeter of the room and feed it with speaker wire (do not split the wire as it stays as is to mimic a 300 ohm twinlead) or 300 ohm twinlead. Depending on the tuner you use a balun 4:1 may be needed.
My MFJ balanced line tuner, Elecraft T1 and LDG Z11 and various baluns all work well with this antenna.
You can also run the loop in a square or oval on a wall or in the ceiling or round a balcony
The SGC manual is another great resource for goofy loop antennas.
Experimentation is your friend here and its no different than the SOE boys in ww2