I used the largest HDX bin from home depot and set it to the same elevation of my pond, it was actually a lot of math because it's fed by a 3" pipe 60 to the pond with a slope on the pipe.....I have an external pump not a submersible pump and wanted all of the equipment behind my shed. but if you have external pumps, you probably know the intake pipe in suction has to be like 2 feet.
most people put the intake bay on the edge or within the pond and make a spillway/scupper/DIY skimmer combination. I didn't want submersible pumps, stuff in the pond etc. you could use an intake bay with an external pump but it gets tricky hiding the pipe, mine is all 2" lol. the naturalized idea is great in principal, it's probably the best solution for water quality etc.