FWIW - here's what I do.
If the overall piece is small I sew all the components together before attaching it to the quilted surface (eg one single flower). If the pieces are bigger (like the tree quilt I have just started) I baste them together and then pin onto the quilt so that when I sew them together I can catch the background fabric and "anchor" it in place.
If you add a thin batt at that stage you get some very interesting trapunto-type effects too, but you need to stitch more than just the edge to be sure that the batt doesn't clump up when washed. Just a few lines through the piece should be enough. Large flowers and character figures look particularly good done this way.
This is a great way to make one block at a time, and also gives the option of putting a completely different design on the back because the quilting is not "interupted" by the applique design. It also gives the option of changing the placement of applique right up until the whole design can be laid out and checked. I can make lots of flowers and arrange them as I would a vase of real flowers.
I started experimenting with this because I could never get a perfect grid around a design ( LOL ) when I was making Rosemary Makhan's Rose Sampler Supreme.
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was my first attempt and a bit experimental, and I hadmy machine stitch set far too short. I now use a longerstitch, esp for gridwork. It looks much nicer. The background fabric for the Tree of Life quilt is 110" wide and has been stipple quilted with no seams. Some of the applique stitching in the centre of such a large piece will be a bit awkward, but I find this method quite fast once you get used to it. And as I prepare all the applique separately, that part of the project will still be very portable.
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OZ Cats are appliqued onto a piece of prequilted blackfabric. What looks like sashings is really just 1/2" stripsof appliqued striped fabric used as a frame for each cat.The background to the Mardi Gras quilt is a diamond gridthat was also pre-quilted. I am interested in seeing if and how others do this type of work.
Good luck Pat - I look forward to hearing what you think of this method.