I let my bunnies have access to the run most of the day and during night time I lock them in.
I have foxes in my area, so my bunnies have to be locked in the cages.
I would say a decent size on a hutch would be length 180, wide: 80 cm. Smallest size for a holland lop would be 150*80 cm, which my indoor cage have that size.
The hight of the cage, should be so high that your bunny can stretch fully on the back legs without bumping into the roof.
In the picture you can see the size compared to my holland lop mix:
My hutch it’s on the bigger side because it’s (length:260cm, wide: 115 cm), really not a smart idea being so wide. Because it’s really hard cleaning the cage, the arms are too short [emoji23]
Make sure the whole front can open with doors, easier when you clean. Myself did many mistakes on my first hutch ever built but at least it taught me what to think about next time. While doing the new adjustments to fix those mistakes.