Greetings and welcome to the board! I personally have not glue basted sandwiches but I have used glue to baste tricky applique which I prefer over starch (starch is sugar and can over time attract moths). You can make sachets from cedar animal bedding but I just prefer to avoid starch all together. Here is a link to a video that shows glue basting for applique circles.
https://www.youtube.com/watch?v=vRLXlELj9zo I think the ironing is just to dry the glue faster. ;-) Reba