Applique pieces
 

My stepmother passed recently, so I was helping to clear out her personal belongings. She was a sometimes quilter, and I was given her 'stash. We found one mostly finished quilt, some notions, and literally hundreds of applique flowers and tulips of all sizes. Some of them have what appears to be dryer sheets to add stability(?). Some have a semi-stiff fused piece with the edges turned over, and stitched with large stitches. Some have been sewn onto a lightweight muslin, then turned right-side out.
On these pieces, there is a slit on the back. My question is: should I leave these as is, with the slit on the backside, or should I trim the backing piece away? If I leave the backing on, would that cause the fabric to weaken, or expand over the years, or would the eventual quilting secure the pieces?

I normally leave the interfacing there so that I can have the extra safety of things not stretching while I am sewing on the applique. Did she use a fusible interfacing? in that case leave it on and press the pieces in place.

if dryer sheets maybe trim, if fusible interfacing it may no longer fuse but shouldn't matter much. when ready, try fusing one to your background, if it doesn't stick, then trim if you want.

applique pieces
 

There was no pattern or picture that we could find for what she intended for these, so we assume that she did them for "busy work". I counted and sorted them again, and there are 100-112 of each type of applique - needle turn, foundation, fused - so she must have intended them for use at some point, she just never got to that point.
She was in Hospice for a short time before she passed, so I have decided to make donation quilts using these pieces. I have several pictures saved on my computer that I want to do (Some day), so this will accomplish both goals - honoring her memory for Hospice, and getting some of my bucket list out of the bucket.