A cake shop has no time slots. It has two ovens, one pair of hands and a day — so capacity is a production day, and a booking either fits in the day or it does not. Asking a customer to pick 3pm on a Thursday is asking the wrong question.
Four slots a day, closed on Sundays. Tap a day to see what is on it.
The one thing that stops a custom cake is not the oven — it is a customer who has not confirmed what they asked for. So the design goes out on a link, and what they tapped is kept with a timestamp against the order.
Two businesses sharing one oven. The counter pays the rent and the ordered work pays for the year — and until they are in one system, nobody knows which is which.