I use these in place of a tempo/LT run. I start off at easy distance pace and hold that for a mile or two - essentially running them as a warm up. I then start cutting the page down.
My goal is to get about 20-25 minutes where I will average out at my tempo pace, with the first part of that being a little slower and the last part being a little faster.
I then finish up with a mile or two at easy distance pace, essentially cooling down. I often set these up as a 10 milers.
I might look something like:
1 - 7:00
2 - 7:00
3 - 6:40
4 - 6:20
5 - 6:00
6 - 5:45 (marathon pace range)
7 - 5:30-5:35 (:05 or so slower than tempo pace)
8 - 5:20-5:25 or so (tempo pace)
9 - 5:15 (closing in on 10k pace)
10 - 6:40-7:00
This is how I'd do it ideally, but often the drop happens a little sooner than I intend. But that mile 6 through mile 9 progression happens at some point (sometimes staring at the 3 or 4 mile mark).
The point for me is, like I said, to get an LT adaptation. But I also get to kind of cycle through the gears some and see where I am and how I feel at various paces, which helps me home in on what my tempo pace actually is. For that reason, I often do this kind of run (sometimes in the form of a 6 or 7 mile run instead of 10) as one of my early tempo efforts. I also do it at then end as a confidence builder since, when you do it right, you get this sense of "downhill running" and you feel incredibly fast closing out a 10 miler at a faster and faster pace, proceeding down to 10k pace or thereabouts.