Lay your outer piece of fabric face-down. Use a pencil or washable fabric marker to trace around template.
Now layer your materials: first the batting, then the inner piece of fabric (face up), then the outer piece of fabric (face down). Right sides should be together. Pin materials, staying inside the pencil lines. Cut out.
Sew materials together around the perimeter of the fabric. Leave a hole for turning right side out. Remove all pins and turn fabric right side out. Use the eraser end of a pencil to poke out all seams. Sew hole shut, then continue sewing to make a decorative stitch around the perimeter of the blanket.
Now we’ll make the holes for the car seat straps. The marks on the pattern should fit most infant seats, however, if you have the car seat available I recommend doing it this way for a custom fit: Lay the blanket in the car seat. Use a pen to mark where the straps are. Remove blanket and use a straight edge to complete the marker line where the strap slits will be. (Don’t worry, the inked fabric will be cut away.)
Sew a box around each marker line, using the mark as a guide for your sewing foot. Use a rotary cutter and a straight edge to cut out the inked centers of the boxes. Then use scissors to trim neatly, but be careful not to sever your stitches.
Lay the blanket in the car seat and pull the straps through. If possible, put baby or a stuffed animal in the seat so you can get a more accurate fit. Fold over the right flap and tuck around baby. Fold up the bottom flap. Then fold over the left flap. Note where the bottom and left flaps meet, then pin Velcro tabs in place. Sew on Velcro.
As with all handmade baby items, use at your own risk. Pattern is for private use only.