I love to make totes...(today is the 14th, and know it will be a while before you get to yours, hugs),...
but I use a piece of plastic canvas for the inside bottom of bag.
I use yarn and 'sew' or 'wrap' the edges all the way around, and then make a quilted cover, and then just lay it in the bottom of the bag.
When you get ready for a new bag, you can take this out and re-use it.
I think old plastic placemats would work out great too.