Opposite (antonym) of peak hour / time
I am looking for a conventional antonym for peak hour.
As far as I've seen, the term off-peak hours is used. Still, to me this means any hour that is not the peak hour, which is not necessarily the hour with the least clients or activity in a business.
Here is an example sentence:
Eight o'clock till nine o'clock is our peak hour; two o'clock till three o'clock is our _____.
Can anybody please help with this?
Consider slack ("wanting in activity").
Two o'clock till three o'clock is our slack period.