Full disclosure: I haven't gotten there yet.
I think I would describe what is not in the immediate play area around the players. Only use the battlefield around players, not whatever some mage is doing off in the distance. If they move, so does the battlefield. Draw the relevant features on some sheets of paper and switch them out when necessary, or erase and draw if you are using an erasable battle map mat.
If they split the party up, use theatre of the mind, even when fighting. You can still roll dice, discuss positioning, and describe the action without a 2.65m circular map on the table.