In the USA the solution requires overtime.
What is missing is the total workweek per person and the work/rest limitations for your location, if any.
If you don't need full coverage during the 1 hour break and each person works a 50 hour week, it can be done by a 6 person staff with interchangeable skill sets.
In the past I've allowed each person to state their preference for work hours each week with any conflicts settled by management.
My assumptions are:
300 = Available man hours (6 * 50)
283 = Required man hours 120 = Critical hours (3 * 8 hrs. M-F)
70 = Mid-critical hours (2 * 7 hrs. M-F)
45 = Off-peak hours (1 * 9 hrs. M-F)
48 = Off-peak hours (1 * 24 hrs. S-S)
Because 10 hour work shifts are not a multiple of a day, divide the day into 2 hour blocks to assign staff. There are enough available hours to provide some overlap and help desk meeting time.