William, I have a method of making flags from Magisculpt that seemed to work on a Civil War vignette I did a while back.
FLAG TEMPLATE
I found that having a form for the flag to cure on saved me the trouble of propping up the flag and getting it to stay in the position I wanted the final flag to be in. The first thing you'll need to do is get some Sculpey and roll it out into a ball. The ball is then flattened onto a piece of ceramic tile (single tiles can be bought at Lowes or Home Depot). The Sculpey does not have to be flattened evenly as you will be making impressions for the main folds which will distort the piece a bit. I do suggest you make the piece a little larger than the size of your finished flag. this will give you a bit of extra working room. Once the piece is laid out you can use an X-acto handle or piece of tube styrene to make impressions of the main folds. To insure the tool does not stick dust the Sculpey with a bit of talk, or give your tool a very very light "skin" of vaseline. After this is done take a ruler and trim what will be the HOIST EDGE (Part of the flag that is fixed to the pole) of your flag. Once that is done bake this in the oven for 15 minutes at 250 degrees. Once the 15 minutes are up let the piece cool in the oven. You can repeat this process 2-3 times to insure you have a solid foundation for your flag. When you bake the piece for the final time and after the piece cools keep the oven open to "air it out". I've used Sculpey in my oven for years and have had no health problem so it's done just to be safe.
The FLAG
Take a ball of Magicsculpt or other two part putty and mix up enough to roll out a sheet large enough to cover the area of your flag. Let this ball of putty sit and cure for about 30-45 minutes. Now take another piece of ceramic tile and give this a light coating of vaseline. This will help your sheet separate from the tile when your ready to place it onto your template. One way to insure your sheet rolls out perfectly even is to have the "rolling pin" or other tool straddle two pieces of strip styrene or basswood with your putty in between. Be sure to give your tool a light coat of vaseline or talc so it does not stick to the sheet. Once you have your piece rolled out let it cure a bit and then cut it to the desired size. After you have lightly coated your template with vaseline carefully peel the sheet off the tile and "work it onto your template. Make sure you have one side perfectly placed on the HOIST edge so it will sit on the pole just right. Let this sit overnight. Lastly boil some water in a teakettle and pour it over the piece after you have placed it in the sink. This will help to break the vaseline bond between your flag and the template and will make removal easier.
If you have any questions just ask.~Gary
PS, The little doodle may help to better visualize the concept.
