This is a frame made from a bent piece of wood. You can use willow, maple, ash, most any kind of wood. Select a branch without forks. Bend it into a "U" shape right after you cut it.
Strings tied across the opening will hold your work. Watch Carol make such a frame, including the different knots, on her instructional DVD titled Introduction to Sprang.
Certain loom manufacturers are making frames for Carol's classes. You can order these frames yourself.
Dewberry Ridge makes Carol's frames, using a clever little tightening device. They make two frames in two widths. Carol usually supplies the 24 inch frame to her students. For a longer frame .... purchase longer dowels at your local hardware store.
Check out https://www.dewberryridge.com/products/sprang-loom
Contact them at: dewberryridge.com
Purrington looms makes frames in a variety of woods, white wood, oak, walnut, and more.
Contact them at: purringtonlooms.com
Egill's Woodstuffs now makes Carol's frames.
Contact Chuck Jones through ETSY for a lovely wood frame.
When Carol was in New Zealand in 2016, frames were made for her South Island classes by Ashford
and by Majacraft on the North Island.