I know what you're thinking-
"Yeah, I remember this- it was called 'biosphere II'"
Biosphere II was an experiment done in the early 90's. It was supposed to be a self-contained ecosystem, and this team of scientists were gonna be locked into it for 2 years.
Biosphere II was a total flop. For
starters, they tried to create a large number of biomes- to replicate the diversity of Earth's ecosystem. They had an ocean biome, a rainforest biome, a plains biome, etc, etc, and a huge number of diverse lifeforms. I think it was probably way too complex to be manageable. However, Biosphere II's main failure was a huge engineering mishap- the concrete reacted with the oxygen in the atmosphere, causing oxygen levels to plummet. The experiment finally had to be abandoned.
My suggestion is a large structure (I'm guessing a geodesic dome) which contains ONLY the minimal plants (and possibly animals, esp. pollinators) necessary for human survival and the continuation of the ecosystem. This would all be planned out by a team of nutritionists, botanists, biologists, ecologists, engineers, and whatever other scientists necessary. Solar panels can be arrayed around the structure to power computers/pumps/whatever else is necessary.
Ideally the inhabitants would be raw foodists, and as high of a percentage of the plant life inside would be edible. They would lead an Edenic life, never having to shop or cook- they just step outside and grab something off a tree. Inhabitants needn't worry about crop diseases, competing predators, etc.
They'd probably have to be sure to take their dumps outside and bury them, in order to plant new seeds.