Montevideo is 3 hours behind Reykjavik
Best overlap: 11:00 AM to 6:00 PM in Reykjavik is 8:00 AM to 3:00 PM in Montevideo.
11:00 AM to 6:00 PM in Reykjavik is when Montevideo is also working, at 8:00 AM to 3:00 PM their time. The 3-hour gap barely gets in the way — you've got 7 hours of overlap, so pick whatever time fits the agenda.