Absolutely! 
Spell jars are highly customizable.
When I make a spell jar, I bop around and grab the herbs/ingredients that correspond with my spell intention, and then layer them into the jar. You can seal it with any color candle wax (again, picking a color that magically corresponds to your intention is an added enhancement) and decorate it if you choose.
Amethyst shared some great spell jar resources- feel free to take a chant or instructions from any of those. If you’re not sure, you can follow them step-by-step, but I would encourage you to feel free to adapt them to suit your needs. Or, you could write your own chant (here’s a guide with tips on how to do so)! It doesn’t have to rhyme or be long- sometimes just stating your wish out loud is all that you need 
Good luck and happy spell jar crafting! 