Find yourself a glass jar that you want to keep your homemade marmite in. Add 2 tablespoons yeast flakes and 2 tablespoons boiling water, and stir well to dissolve them (I use a chopstick).
Add 5 tablespoons of black tahini and 3 tablespoons of miso to the jar and stir everything together so it's mixed really well.
Eat and enjoy!
Store in fridge and to be safe, I'd try to eat it all within two weeks or so. If you're not sure you'll eat it that quickly, perhaps make a half batch first...