Step one. Fabric- I bought 4 different fabrics each 1/3 of a yard. This is enough to make 2 banners, but you need the length so 1/3 is the smallest I could buy for my banner to be the size I wanted. I made each triangle 12" wide at the top and 13" in length. After I had one cut out I layed it on top of the fabric and used my rotary cutter to cut the next one. I cut 3 triangles in each fabric, but only used 10 for my final banner.
I don't have a picture of this next step but I used grosgrain ribbon and sewed the triangles onto the grosgrain using matching hotpink thread. I think hot glue or fabric glue would work just as well though. I didn't back the fabric or anything. Unless its backlit by a window, it's not necessary. Here's my finished banner- and let me just say she loves it!
The cost of the project was $8.10 for 1.3 yards of fabric and 5yrds of grosgrain ribbon. It only took around 30 minutes to make & I can't wait to make more for my other two kids. I think this would be great for baby showers & birthday parties too. So easy & fun!