Instead of unpicking to reuse the piece, I just use a different colour of thread, that way I used the same piece a few times, trying out different designs.

You can also practice without thread, to get the motion down, and reuse the same sandwich many times. Then move on to practicing with thread.

I go to the thrift store and buy sheets and fleece blankets. Cut to size and sandwich then draw squares, triangles etc on them and practice fmq. Saves on paying a lot for fabric and batting.

I think it is a good idea to use contrasting color thread, so you can see where you've been. I like the idea of not using any thread, as Mitty suggests, too.

I use ugly fabric that I know will never go into a quilt.

Someone here on the board in about the last two weeks or so suggested using water soluable thread which I thought was a great idea!! I picked out a small sandwich (about 18x24") and I'm not too eager to do that again. I used muslin I got on sale. There were a couple of good ideas here too. Good luck on what you try.

Years ago at a AQS quilt show I found this package of different types of batting. I bought this specifically to practice my FMQ on, the squares are 18 inches and I just sandwich with any fabric I'm not trying to make a quilt I'm just trying to practice. Although I could have made a quilt out of it that wasn't what I wanted to do.

That’s what I use. Cheap muslin and batting Square sandwiches

You could use these practice panels: https://www.heartbeatquilting.com/sh...ric-Panels.htm

If you use water-soluable thread in the bobbin, you'll be able to soak the panel in water and reuse them as many times as you wish. Be sure to remove the water-soluable thread bobbin when you want to sew something that you want to keep.