I forgot to mention there was a patent filed in 1892 that shows the use of zigzag stiching as a method of appliquing stars to a flag. See here: https://patentimages.storage.googleapis.com/de/38/d5/1f718ef5a97831/US469395.pdf
Also if you do a Google search on Thirteen Star Flags by Grace Rogers Cooper you can find a digital copy of it too.
Cheers,
michael