Sticky.
 

Question. I have stuck a block of applique onto the wrong side of the backing .

Is it possible to unstick bondaweb?

I'm not sure what bondaweb is but if it's like stitchwitchery, try rubbing alcohol. I bought a pair of shorts that someone had put cuffs on with that stuff and I don't like cuffs. I wet the material with the alcohol and scraped the residue with my thumbnail. It took a while but it did come off.

I feel your pain - easy done! You could try gently re-heating the block and try to peel it off. Try a small corner first. Sometimes the fabris begins to fray, in which case it probably won't work :(

In a panic mode, I think I would probably apply another piece of the fusible on the back side (which is the right side of the fabric), cut out the shape of the applique (there would be several thicknesses though) and re-apply it to another piece of fabric. It will probably be a little heavier because of the extra thicknesses. I know this sounds crazy, but....

Thank you. Unfortunately GailG I thought of this but I am hand embroidering over the top and needle is too difficult to use.
I have tried peeling as suggested this worked very well on the large pieces but frayed terrible on the thin stem shape.

Managed to make a new stem and finished the block

Dotty, sure do like the block. Glad you were able to save it.