You can frequently find Rice by foraging grass tile 1-2 tiles beside water tile or on marsh tile. It is possible to find rice on other tiles or distance but it will be rare occasion.
Rice can be planted in shallow water like reeds. The required depth of water for sowing is around 3-4 dirt. Fields can be sloped.Rice fields can be tended, harvested, and rice sown like other crops.
Note that 43 foraging is needed to forage on Marsh tiles.