A lady at my barn likes to make homemade horse treats and gives them out once in a while to all the boarders. I've even ate one before haha and it wasn't that bad :P
It was like, a cookie with some stuff in the middle. It included like some carrot shreds, crushed peppermints, and some oats or w/e to mix it all together. I'm sure there are some recipes if you search on google :)
Also you could make beads to put in your horses hair, just for the fun of it :p I've heard people use beads not only for decoration, but for rhythm beads. I think it's to help with your timing with posting I'm guessing? Maybe adding a jingle bell on the end would be cute :)
Or if you really are bored and not sure what to make, you could Youtube things to do with your horse..if you have one. When I was really bored in the winter and couldn't go down to the barn a lot, I would Youtube how to teach my horse how to bow, how to french braid the tail (which I learned from Youtube
), how to button braid.
There are a lot of things to do if you get really bored, it all just matters what you're interested in.