I have sewn a tote bag which can accommodate A4-size books.
I tried to iron the fusible interlining fabric but it seemed not working at all. It did not fuse to the wrong side of my outer fabric. Anyway, i just sewn it.
The tote bag has a flat bottom of 6cm.
Pens can be stored in the pocket inside.
I sewed the whole bag by hands only instead of sewing machine. I was worrying the seam line not tidy enough. Finally, it looks fine!