I’m sharing three decks here. All of them last 15 minutes, but you can make them longer by duplicating the slides and changing the number that is typed on the slide. The transitions are built in and will carry over when the slide is duplicated. This allows teachers to write in what task the students should have completed at that time.
The last deck doesn’t have the text boxes, so this is useful if you just want a timer. Download this deck here.