You are very welcome.
Please notice that Nolee's lovely avatar is another good use of scraps.
The purpose of the foundation is to hold the shape WHILE you put the block together. You could use old (ironed) newspaper pieces and have the work of tearing them off. I decided to use batting scraps both because I have them and because I am going to need batting anyway. The drier sheet won't fall apart, but if it did, the fabrics are sewn to each other and are as strong as any pieced quilt blocks.
What I used to use was squares of freezer paper. I got tired of pulling them off again. Also, 18.5" (the width of my freezer paper roll) turned out to be a bit on the wide side for the sort of effect i wanted.
BTW, I have made blocks that incorporated the sashing. I brought the scrap pieces to a sashing width from 2 edges of my foundation, then put the sashing directly on each block's foundation. For me, the making, folding the foundation back to trim, etc., was much harder than backing the sashings separately. Of course, if you are using you drier sheets or other fabric foundation, the whole question does not arise.
One time, I used puffy poly batting scraps for the block foundations, sashed normally and used a low loft batting under everything. The poly batting was very awkward ro work with as a foundation, but the results were very cute and cuddly.
I read somewhere that someone used sheets of the water soluable interfacing for scrappy blocks. To me, that seemed to be a way to throw your money away, since almost any fabric is cheaper per yard.