I found two different tutorials by two very crafty bloggers.
Homemade by Jill entered her design in the So You Think You're Crafty competition. Jill's tutorial can be found here. The other tutorial, (the one I used), is created by Sharla at My Little Gems. Her tutorial is found here.
Unfortunately, I did not have any hotwheels for the photoshoot (my girls do Thomas, but not Hotwheels).
And here it is all rolled up
The car fabric is actually a thrifted Pottery Barn Oscar sheet scored at Value Village ($4.99).
If you are looking for other possible fabric choices, here are some options:
The "Traffic Jam" collection by Allison Jane Smith
Via the Fat Quarter Shop
Ikea's Vitaminer Bil
My personal favourite is "the Wheels Collection" by My Mind's Eye (Riley Blake). This collection was released on January 21st and has just arrived in My Needle and Thread's Etsy Shop. Here's just a small sample of what I think is probably the coolest fabric for little boys!
And another well-priced option is the Oh Boy line by David Walker available at Cotton Thread Fabric's shop