The Sea of Stars
Shards range from the size of Manhattan all the way to the size of a planet (characters wouldn’t have the concept of a planet), and often have ruins that indicate they were once part of a larger world at their borders (most literally just have an edge you could drop off).
Many do not have enough of an ecosystem to sustain proper weather (clouds, rain, etc) (At least one of the 13 kingdoms is the size of Africa, and has weather). Waterstones are special rocks that constantly generate water, and can be found at the base of, and along many streams. Travellers often put a Waterstone into their waterskin to fill it up.
The fey, some kind of other realm entirely, exudes luscious plany growth that is often much healthier than those gained from the stars, and places where the borders to the fey are thin provide the most arable land. Unfortunately, these also have the highest chance of allowing people to accidentally wander into the fey, or for fey creatures to escape into our world.