But it’s a major pain to knit a border on a large piece of knitting like an afghan (or even a baby blanket) once it’s been knit. (Yes you could do something like applied I-cord or knit the border on as you go, but it’s still not fun.)
An easy solution is to add a crocheted edging. As shown in that tutorial, I usually do single crochet, but once you’ve got a round of single crochet done you can build off into any complicated or simple pattern you like. Crocheting a border is a great way to add a contrasting color, and if you make it big enough it can weigh down stockinette edges and keep them from curling.
Have you ever done crochet with your knitting? I’d love to hear what you did and how it turned out!