When I had one baby here is how I napped- took baby into bed, closed our dark curtians, and nursed sidelying. I usually took a book with me (I have read myself to sleep all my life.- If the room was too dark, I used a booklight.) Soon baby and I would be asleep. Here is how I get naps now that I have 3 kids and cannot go hide out in my room for an hour: I sit on the couch. I lean back. I nurse baby. Baby goes to sleep, safely on top of me. I close my eyes, and I am asleep, at least for a bit.
While of course darkness helps for longer stretches of sleep, we (humans) are able to sleep during the daylight hours. Entire cultures do so routinely.