I've done it! I've made a crochet rectangle which I've folded in half to make a pouch, crocheted up the sides and done two hanging loops. It's a thing!
For a long time I've been meaning to come up with something better than attaching party invitations, school stuff I need to remember and so on to the calendar with a paper-clip. For one thing if I do that the bits of paper always cover up something I need to remember and for another they fall off in the slightest breeze, such as that created by a ten-year-old running past. Now I have my crocheted pocket and I am Organized!
It may be slightly wonky (though much less than it would have been a week ago) but I'm very proud of it. Thank you to commenter Anon for all your help!