In high school I used to sew wallets for my close friends. I modeled them after my brother's '80s velcro wallet he'd left behind when he moved out. My wallets were hastily made, often crooked, but they were made with love and I always stitched my friends' names or initials on the overflap.
Fast forward more than a decade. I'm starting to get back into sewing and I'm about to leave on a trip to New York. I purchased at the thrift store a red, watermelon slice-shaped sling purse and I couldn't fit my checkbook wallet inside. So I decided to make one.
Making a wallet takes some planning. You have to know when to sew what so you aren't left with unsewable raw edges. I like to map out what I'm going to do and when I'm going to do it. I use construction paper and cut out all the wallet's components and make sure I leave enough seam allowance to still fit credit cards in the slots (I failed on the left-side slots as you can see below). I lay out my paper wallet so I can physically see how the wallet is assembled.
My wallets have a long pocket down the middle for bills and two pockets inside which have credit card slots sewn on top of them. They velcro close so I have to sew the velcro on first since I can't sew it when all the pockets are assembled (you'd be sewing the pockets closed).
First I iron interfacing to all the wallet pieces. For the main body of the wallet I use heavy interfacing and for the pockets and slots I use lighter weight interfacing.
Next step is to turn down and sew the top edges of the credit card slots. Iron, iron, iron! It's the only time I ever iron is when I am sewing. It makes crisper edges and everything is easier when you iron.
Next you turn under and sew the edges of the inside pockets. I like to baste all the inside components together before the next step, which is to turn down and sew the long inside edge of the pocket.
You can see in the wallet above that I skipped a step and had to hand sew the right-side pocket closed. I failed to sew this down before sewing the outside to the inside. Too late once it was flipped!
Then only other thing I'd do differently when I sew the outside to the inside is instead of leaving an open seam and hand-sewing it shut, as I would a pillow, I should just leave the whole top edge of the wallet open and then turn it under and sew it down once it's right-side out.