I make them in 8 ply yarn which in the US is DK/light worsted and in the UK is known as DK. I use a 4.5 or 5.0 hook and crochet 10 rounds. This works up to about 10 inches but don't worry too much about the size as the yarn is very flexible. I ask for 10 rounds as I crochet the squares together and it's easier if they all have the same number of rounds. I use 35 per blanket in a setting of 5 by 7 squares and it will measure about 50 by 70 inches when finished. I crochet around the edge of the whole blanket when it's joined together.
I've been making and donating quilts and crocheted blankets for many years now and usually give anonymously so don't always see people's reactions to being gifted with a quilt or blanket. However, I did hear from one agency who were distributing quilts and blankets to disadvantaged young people. They offered a quilt to a 17 year old young man and he'd spotted one of my crocheted blankets and asked if he could have that instead as it reminded him of one his Nanna had made years ago. Of course they gave it to him and offered a quilt as well but he said he didn't want to be greedy and was just so happy to have a blanket to remind him of his Nanna.
You just don't know what our hand made items can mean to someone who has very little, especially if it reminds them of happier times.
So I hope I have answered your questions but ask if you need more help. I call these blankets Licorice Allsorts as they remind me if those lollies. Also if you need an answer to a question could you please address it to my email address at email@example.com as listed on my blog as I can't always answer if a post comes through as anonymous or if your email address isn't linked to your blog. It was lively to hear from you Sarah and the answer might help some other readers too.
Hugs, Jan Mac