When he went out to get the pizza, my step-dad used to wrap his coat around it to keep it warm (meaning he was cold!) and so I made him an insulated bag like the delivery guys (and then his neighbor liked it so much I had to make another one). Fast forward several years and the original bag had suffered a bit of damage (it sort of melted against a hot pipe). So, I made another one for him! I couldn't remember how I made the first one (and they don't live nearby), so I winged it, and messed it up. So, I started again (carefully unstitching the first one) and was a bit more successful.
While I didn't take any progress pictures, here's a basic outline of how I made it.
1. Buy a pizza or two so you have boxes to measure (my bag is made for two Rustic Pizzas from Papa Gino's).
2. You need the following measurements:
-The width of the box
-The length of the box
-The height/depth of the box (times 2 if you plan to carry 2 pizzas)
3. You need to following materials:
-Outer fabric (I used nylon flag fabric)
-Cotton batting (or foam padding) for the insulation
-Heat-proof fabric (I used the silver stuff usually used for potholders and ironing board covers)
(Optional: Instead of the separate batting and heat-proof fabric, you might be able to find something for making insulated shades that has the pieces already stitched together... but it's usually more expensive... but it would save you a lot of time)
Double-fold bias binding
Sew-on hook & loop fastener
4. From each material, you need to cut the following pieces:
Side pieces: Add an inch to the height/depth measurement for seam allowances (and if you want, add another inch for wiggle room), and a half an inch to the length measurement (and, if you want, add another inch for wiggle room). Cut two rectangles (from each fabric) that fit these measurements. If desired, secure the batting to the heat-proof fabric with some rows of "quilting." Or, just use a lot of pins...
Main body of bag: Add an inch to the width measurement for seam allowances (and if you want, add another inch for wiggle room). That's the easy part. For the length of the body of the bag add:
The length of the box X 2 (and if you want, two inches for wiggle room)
The depth of the box X 2 (and if you want, one inch for wiggle room)
4-6 inches for the last part of the flap (part of the flap is the taken care of with the second depth measurement... this measurement takes care of the part that overlaps the bag to keep it closed)
Cut 1 rectangle (from each fabric) that fit these measurements. If desired, secure the batting to the heat-proof fabric with some rows of "quilting."
5. For each section (the main body and the two side pieces), pin all three layers together to make a sandwich (outside fabric, batting, heat-proof fabric), and baste (or zig-zag) together about 1/4" from the edge.
6. Now you will attach the side pieces to the main body of the bag. Putting the outside fabrics facing together, line up one long edge of one side piece with the edge of the long side of the main body part, wrap it around the short end of the side piece, and back up the other side of the side piece. You should have material left over, which will form the entire flap. Stitch through all layers (the raw edge of the seam should end up on the inside of the bag).
7. Repeat step 6 for the other side piece.
8. You're almost finished! Now, attach the bias binding to the raw edge along the top of the bag and around the flap (you can zig-zag the raw seams if you want, but I never did). You're on your own with the best method for attaching the bias binding because, as you can see in the photo, I am not very good at it
9. Finally, decide where to put the hook & loop fastener for the bag closure (refer to photo), making sure that you allow for the depth of the bag when full of pizza.
10. Enjoy pizza that is almost as hot as it was when it came out of the oven!