One of the swaps I was recently involved in required the swappers to make a drawstring bag, following a named pattern, for our swap partner. I've made drawstring bags quite a few times, but this one had a lining and box corners. I'd lined a couple before, but more by luck than judgement (except on those made from a circle of fabric, they're simple to do), but I'd never done a box corner before!
I forgot to take a photo of the bottom of the bag, but you can see the squared-off corners in the first of the above photos. The pattern we used had clear photographs and really well written instructions, making the bag straightforward to make, including the box corners.
You can find the tutorial I used on the 'In Color Order' blog.
My bag wasn't perfect, but it did turn out to look like the ones in the pictures! To add a bit of 'me' to the bag, I added four puffs, evenly around the top.
I do aim to make some more of these as they are useful for storing stuff in. I'm keeping my knitting in one of the ones I had from the swap (I received two from my partner). That's something else added to the ever growing 'to do' list!