Extending/adding on to a finished piece.

[Jan_in_CA]

Here’s an old thread where you asked the same question (basically) maybe some of the comments will help you out again now.

Adding knitting onto ready-made clothes

Salmonmac, what excellent information…I haven’t clicked onto those sites yet, I’ll do it later tonight, tho. Thanks for getting my imagination rolling in that direction! It’s funny, sometimes we can read a bit of this 'n that, (knitting related, of course, and in this case your this 'n that!) and suddenly our minds expand and make connections to other ideas. That’s how it works for me, anyway. Maybe I’m just weird. Rochester, Thank you, I never would’ve thought of that! I’ll probably make…

These ideas may help, too.
https://www.craftsy.com/blog/2015/06/how-to-attach-fabric-to-knits/
https://www.craftstylish.com/item/9107/how-to-add-crochet-trim-to-any-fabric-edge/page/all