For labels, I would consider making a 2" height, by 2.5" or 3" piece. This can contain the info about the print, and price and your contact info.
I tend to place a small version of the image in question in the upper left of the label. Use a border around it, any of the border actions will work
or you can just make one up. I print these on matte paper as you can't cut RC as well and the matte paper is just easier to work with.
Batch them, on letter size 8 per sheet, or you can just make a custom page and run them all at once off roll.
Attachment, many methods will work. If the work is framed, I would use a piece of string and let the label hang. Tape to back of print and back
of label. You can also tape them to the front of the glass, however if you do this, I would go a bit smaller to not cover up too much of the work.
Just one way, there are many others I am sure.