Here's what you need:
2- pieces of fabric 35" x 44" (I used cotton for the top and flannel for the underside. It's cold out there!)
4- strips of fabric 2"x 8" (I used the same pattern as the top cotton, but you could totally go for coordinating fabric)
2- 2" pieces of Velcro
1. Sew your two fabrics right sides together, leaving about a 7" gap
2. Clip your corners and turn you fabric right side out. Press.
3. Sew all around your blanket. I also typically sew an extra line closer to the edge to really secure that opening.
4. Figure out where those straps are going to go. To do this I placed the blanket on my carseat and felt around for where I wanted them to be. Mark this with with your marker. Mine ended being about 9" apart, but carseats vary so much.
5. Sew two strips right sides together, leaving one end open for turning. Repeat for the other strap. Clip your corners. Turn and press, making sure that you press the opening to the inside.
6. Sew all along the outside of your straps.
7. Sew your Velcro on each strap about a 1/2 inch from the ends. Be sure to sew the corresponding Velcro piece to the opposite side of the strap.
8. Mark your strap where you will be sewing. I drew two lines about 2" apart. Place your strap on your blanket. Pin and sew.
9. Attach to your carseat and admire. Apparently my friend's carseat is black, white and red, so this is going to look so fun with her carseat.
Please comment if you have any questions at all. I would be glad to clarify any of the details if necessary. Oh, and please let me know if this tutorial is useful to you. I look forward to doing more tutorials. I have a few in the works right now;)