(based on this pin)
fabric strip, 1 yard x 6 inches
elastic, 1 yard
sewing machine, scissors, thread, etc.
1. Measure the length you'd like the sling to be around your little guy.
2. Sew a strip along the length, wrong sides together. Flip right side out.
3. Pin elastic along length of sling. Sew parallel lines about an inch apart. (You can measure them meticulously or just eyeball it like I did. It works at varying widths because some cars are thinner than others.)
4. Place cars in slots. Watch happy child play!
*Warning: Can get a little heavy when fully loaded!