I was going to write a tutorial on how to make them but there are already so many tutorials out there. Here are some of my favourites for similar bags:
with interfacing and an easy way to sew gusseted corners
with French seams and a pocket
a simple unlined bag
And while I was at the market, I couldn't resist buying a bunch of poppies. I love their weird hairy stalks and tissue paper petals.
Reading: All at sea - biography by British journalist Decca Aitkenhead about life before and after her husband died while saving their son from drowning