I used strava to help me find 2-5 mins climbs in the area. And I just vary the repeats for my Vo2 efforts.
For everything else find something flat if you can unless you have 10-20 min climbs near you.
I’ve got a good 10 mile out and back unfortunately has a couple lights in it.
There’s nothing wrong with having a longer than ideal break between sets.
I find it’s 20 mins to the first hill which is a 3 min hill. Then the loop back is like 3 mins. X 3 bike back closer to home 15-20 mins until next hill. 2 mins x 5
If I’m doing ss I’ll use the flat route. Just get comfortable using the same segments.