Sure!
Take a jar. Any size, but hey might as well make it in a big batch, amirite?
Fill ¾ full of dried arnica flowers. fill the last bit with rosemary, and throw a few dried hot peppers in there. Fill jar to just below brim with oil, whatever kind you please. Jojoba, almond, olive, whatever doesn’t matter.
Now, let sit somewhere warm for about 6 weeks. (If you want it sooner, plop the jar in a pan full of water to make a makeshift double boiler, and heat on the lowest setting of your stove for 2-3 hours.)
Then, strain out plant material. Add an ounce of beeswax or plant wax for every five ounces of oil (less if you want a softer texture, more if you want it harder). Put oil and wax back in double boiler jar, and heat until wax is melted. Stir, and then pour into containers and let cool. There ya go!
It will keep, if kept in a cool dark place, for at least six months. Probably longer, but I’ve always used a batch by that point and made a new one. If you wanted to pop it in the freezer until you needed a jar, it would presumably last basically indefinitely.