Step 1: The first rib
The first step was to make a semi-circle from 1/8 inch rod. (red arrow) I scribed an arc onto a piece of scrap plywood and sawed it to make a bending form. I intentionally made the arc with a radius smaller than the final arc because I knew the steel would spring back. I should have made the radius about half or two-thirds the final desired radius because it sprang back considerably, and I had to finish forming the arc by hand.
The original black portion of the plant hanger is coated with a rubberized covering. I had to file through it to get to some bare metal for welding. I clamped the rod arc in place and welded it with a flux core wire feed welder. Flux core wire can dig through dirt and contamination a MIG welder cannot.
Step 2: Anchor piece
Step 3: Add a solid rib
Step 4: Make a second anchor arc
Step 5: Add ribs of steel wire
Do the same for the ribs on the flat back portion, but straighten the wire pieces first.
Clean away powder marks from the welding flux. Paint with black spray paint. Hang and insert the fibrous blanket that provides a growing environment for the plant roots.