I thought I'd show the back of an orchid piece, with the hanging mechanics that seem to be working for me. Here's the top of the back with a few notations. The hanging "sleeve" is essentially an upside-down pocket handsewn onto the back facing. A piece of foam core (cut to size and edges taped) is slid up into the sleeve. The hanging wire passes through 2 holes in the lower corners of the foam core, about 2" up & 2" over from the corners. I used coffee stirrers to reinforce the holes. The wire runs through these and is twisted together and taped down on the backside of the foam core. Small gold safety pins hold the wire to the sleeve so the piece doesn't flop forward when it's hung.
On the bottom of the back, there are 2 triangular "pockets" into which a narrower piece of foam core (again with taped edges) is slipped. This overall piece is a little under 24"x36", which means a 20"x30" piece of foam core isn't quite wide enough to be used as is. By cutting the top piece of foam core to about 23"x17", there was enough leftover to cut the "weight" for the bottom. -- PJ--