For changing pace and telling over time within a dramatic scene, you need to back off from moment-by-moment presentation:
For the next ten minutes, Harry was busy hammering in the remaining tent pegs.
It took him ten minutes to hammer in the other tent pegs.
Over the next twenty minutes, the rock took on a sharper form. It was even odder than she’d first thought …
Naming an amount of time works, and so do vague equivalents like ‘a long while’. Or you can back off to an out-of-the-moment level of understanding:
It was even more difficult finding cracks for the next three pegs. By the time he’d finished, Harry was sweating …
Harry hit his thumb another five times before he finished the job.
Volusia returned to the iron box without a struggle. (The Black Crusade)
Here, you’ve shifted from a focus on the action to a focus on something about the action. Not hammering in the tent pegs, but the ease or difficulty of hammering in the tent pegs. It’s a sleight of hand, like the magician who draws the audience’s attention away from where the trick is really happening.
There are many other angles you can work. As an exercise in creative writing workshops, I give out the texts of separate dramatic moments, then challenge the participants to invent ways of bridging quickly and smoothly from one to another. I usually end up learning more than I teach.