I did a similar method years ago when I was making a tree skirt. I used the Spectral Designs pattern: Pointsettia Tree Skirt. I drew the pattern including the leaded glass on freezer paper (reversed), carefully cutting out all the "glass areas" and ironed to a larger piece of solid black fabric. One color at a time, I cut between 1/8" - 1/4" inside the line (within the colored area), snipped the curves and points to within a thread of the paper, and used Quilters' GluTube rubber cement to glue the seam allowance and the paper surrounding that color. Since this is a rubber cement product, you have to allow a few minutes for it to set up and get tacky. Once "dry" I used a tooth pick to turn the seam allowance over onto the freezer paper. Once you have that colored area done, you lay your colored fabric right side down, flip and stitch by hand or machine (I used a small zig zag) in black thread only on the "leading" and it is almost invisible and each shape is perfect. Trim the back colored piece close to the stitching and repeat. Here are a few pictures to explain a bit better.
[ATTACH=CONFIG]527740[/ATTACH]"colored" area has been cut away from the freezer paper pattern (reversed)
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front view of red and yellow sections sewn in place
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back side, showing stitching and trimming
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glue I used. Hope this helps. You are on your way and it looks great, but this may be easier.
Here is the completed wedge:
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