This graphic may give you some ideas of a methods you might use. Please think outside this box and come up with alternatives that suit your process.
You could piece all the blocks together with either method, then apply the sashings as long strips. Or do individual blocks with sashings on two sides, then add long sashing to join the rows of individuals together.
You may even come up with another way to hasten your process or one that works better for you.
I envy you the chance to work on your mom's blocks.
I taught my own mom to quilt and I was the first quilter that we know of in 5 generations of my family; no unfinished treasures to love and cherish.
Jan in VA