I would place a layer of WSS on top of the flannel to keep the stitches from sinking into the fabric.

I use tear away on the back of flannel with temporary spray adhesive to hold it firmly in the hoop.

Try using the sticky back stabilizer,and wash away on the top ,i find it works very well.

Have a look through the embroidery library tutorials, they are really great. I am using cutaway stabilizer more now, it really does make a difference to the stitchouts. Obviously sometimes other stabilzers suit the project better, but if your having difficulties, try it with cutaway and see how it turns out.

Flannel is very stretchy it does not seem like it but after quilting with it for years I know thin. I would tend to use a good ( med to heavy) cut away , baste around design and spray adhesive to hold in place. Felt does not often even need stabalizer as it is very dense. Hope this helps Lisa

I've made several flannel quilts and always have used tearaway, med weight and hoop everything. don't pull to tight on your fabric will pucker when you unhoop. Has worked great for me so far.

Try stabilizer the both sides. I never done , but I've heard at a stabilizer site. The fiber stabilizer behind, and water soluble in front of it!