Summing up and adding a bit:
► Soak it for a couple of hours before doing anything.
► Carefully remove the pot, breaking or cutting it so that minimal root damage occurs.
► Extract as much of the current potting medium as possible - again, with minimal root damage
► Line a much larger basket (12", maybe) with sphagnum.
► Place the root mass in it with the plants hanging off to one side.
► Fill in with more sphagnum.
When you attach wires to the new basket, the two front ones can be a few inches longer to hold the basket at a 45° angle (or whatever, as needed to keep the plant stable).
The basket below was at 90°. Sogo Redfox, a gigantea hybrid.