I started making my own tempeh four years ago. It took me a while to figure out a good method, but now the entire process is easy and relatively quick — almost always a total of 72 hours from start to finish. The effort involved is on the order of making scrambled eggs, though there is a longer wait between steps.
I make tempeh from a 50-50 mix of (intact whole) grain and legumes. The photo shows a black-bean-and-black-rice tempeh. My most recent tempeh was soybeans and 3 grains (counting quinoa as a grain):
1/2 cup sprouted tri-color quinoa
1/2 cup sprouted millet
1/2 cup intact whole einkorn
I store the finished slab of tempeh in the refrigerator and dice it (large or small, depending) for stir-fries, chili, stews, curries, soups, etc. I also spray the diced tempeh with a little olive oil, tossed with some spices (smoked paprika, ground chipotle or cayenne, etc.) and salt, and then roast that in the air-fryer for a snack.--