If you got access to earthworms, make a box or use a large container. fill it with moist dirt, no sand. Mix in some vegetable scraps, old coffee grounds add as many worms as you can. Cover the top with very dried goat poop and keep moist cover with a fabric, something breathable.
Keep it moist, not wet, make sure you have good drainage out the bottom, keep from extreme temps, it doesn't have to be steady just no extremes either way.
Give them a season and you'll have very good soil, considering your situation. You can flush the soil after use and mix it back in to the container. mix in more scraps and grounds as they compost it, and mix in the poop as that deteriorates. layer a bit more on top.
You can also rig something to collect the drainage to use for a "tea"
It's obviously not the perfect way or the best, but it will work and you can adapt from there to make it better for your situation.