I think I read somewhere about rearranging plant's roots in certain ways within the soil inside a pot to make it think it's growing in a larger space, and as a result let it grow bigger, as if it was planted in a large pot. I don't remember any details, and what I've tried so far hasn't shown significant results, so I'd like to know if it's even possible to achieve this effect − make the plant grow larger without increasing the soil volume.
I think one of the ways was to make horizontal layers where water would accumulate like on the bottom of the pot, effectively increasing the number of "bottoms" inside a pot, but I couldn't create such a structure at home.
Ultimately what I want to achieve is to grow larger plants on a small balcony (or window sill) with limited space for pots.
Currently I have two citrus plants growing at their limit of 1.5m (5ft), due to available soil in their pots, 20cm (8in) deep, 20cm (8in) wide, and I'm also planning on planting golden raspberry and almond from seeds. My available sill space is 80cm (31in) by 20cm (8in), and ~2m (~6.5ft) in height, and the balcony space is roughly 20cm (8in) by 4m (13ft), but the cold days have started and I've moved the only 2 pots I care about to the sill. I'd like to at least grow the almond seeds now and repot them closer to spring into bigger pots, and then maybe move them to the country house's grounds next year. We'll see how that goes.