Hi there, I just recently made my first ever afgan using that yarn! I based the pattern on a HUGE one my grandmother had made me years ago and it's super easy, It's basically a bunch of dishcoths connected together.
What I did was make 16 "dishcloths" using the basic pattern (I think it's called grandmother's favourite discloth) in 5 different colours. I used 8mm needles and made the "cloths" 25 stitches wide at the widest point which makes the squares about 5 inches on each side. Then when they were all done I crocheted them together with the left over bits of yarn from the squares, but it can be sewn together too (that's how my grandmother did hers), which ever you preferr.
The squares take about an hour or 2 each, depending on how fast you knit and joining it all togehter takes about 4-5 hours. I'm sure you could quite easily make basic squares as well but I like how the border on the discloth, and the diagonal stitichs ads a bit of extra pattern to the blankie.
I made this for my year old neice using pastel pink, purple, blue, green and yellow yarns; it ended up looking like multicoloured cotton candy, and it's SOO squishy!! Unfortunatly I wrapped it up for christmas before I remembered to take a picture, but the next time I got to visit her I hope to get a pic of her with it.