I don't generally pre-interface fabrics (more about why shortly...), but I think it's a pretty common practice. A search didn't turn up much info online, but perhaps my search terms need some improvement.
Anyway, I bet a lot of you already apply interfacing to your fabric and then cut out the pieces--at least some of the time. With the card wallet pattern that is coming soon, pre-interfacing your fabric is a great option.
I've found myself pre-interfacing the fabric for these card wallets because the small pieces are just so much easier to cut out with some accuracy.
It's is also great for using up small scraps of wrinkled interfacing. You might have seen me mention I iron my interfacing on, rather than "pressing" it like the instructions indicate. I've been ironing it on for years and years, and it works great. It doesn't matter how wrinkled a piece of interfacing gets, it can be ironed on and still get smooth results. BTW, ironing interfacing on probably works best with woven interfacing and not the non-woven kind that is compressed fibers.
In the past, I haven't been in the habit of pre-interfacing because it does waste some fabric and interfacing. For small things, the waste amount is minimal, but if you were to interface large sections of fabric you could end up with a lot of waste. That would be sad.
Plus I'm just stuck in my sewing ways! But sometimes I do manage to break out of a rut and develop a new habit. So at least with the really small things, pre-interfacing might be my new preferred method. I'll probably still write the pattern instructions for cutting the pieces independently, but pre-interfacing is always an option.
After some experimenting, here is the method I've found works best for me:
1. Place the pattern piece on the interfacing & cut around the general outline of the pattern piece.
My pattern pieces are chipboard, so they are fairly rigid, which makes this part easy. If your pieces are paper, you might find it easier to trace an outline on the interfacing and then cut it out.
I don't cut it the exact shape of the piece because it defeats the purpose of giving some extra stability when cutting the fabric pieces out.
Cutting each piece separately seems to go faster, and when using scraps, I can just compare the interfacing to my scrap fabric and see if it's going to fit. I tried doing one bigger piece of interfacing that would fit all the pieces, but found myself digging around a lot trying to find a big enough piece of fabric, and it just didn't work out very often. Plus the larger piece sometimes was an odd shape that didn't fit efficiently on the fabric and it seemed like I wasted more fabric.
2. After applying the interfacing, cut the interfaced fabric sections away from any remaining fabric.
I don't want to get this fabric out later and find interfacing adhered to it, and cutting the fabric/interfacing away before cutting out the pattern pieces is easier.
3. Then just trace and cut out the piece(s).
