Before you try wedging at home, be sure that the place where you wedge (ie table top, counter top, etc) is VERY sturdy. Most home furnishings will not stand up to the stress of wedging.
As to the actual wedging surface, you can staple material (couldn't find canvas so I used denim) to a board with staples on the bottom. Be sure to put something under it to prevent the staples from injuring the surface you place it on.
However, I prefer to wedge on plaster. You can make a tray from plywood and 1" by 2" boards and fill that with plaster or you can make a full wedging table, using the tray as the top. The table must be very sturdy.
When the school where I studied pottery (Cupertino, California, USA) bought commercially made wedging tables, they collapsed after a few weeks. Our teacher then made tables using 4 x 4's (that's 4 inches by 4 inches), 2 x 4's plywood, and plaster. That was about 15 years ago and they are still standing today. Unfortunately, I don't have the plans. Maybe somebody out there has a good set??
Jan C.
Jan C.