Planning restrictions could be modified so that it is permitted for people to buy land and build on it if they wish, most would probably be solo, but group builds should be seriously considered, I’d go so far as o say they they should be encouraged for first time home owners as an affordable option.
Planning laws seem to be far too draconian for example only allowing you to extend your property footprint by 10%… planning permission could be required to make sure that people do only reasonable size for the surrounding area, but should take into account the reasons, for example a blended family with a large number of teenagers with no bedroom.
We could also make it easier and more affordable to build a granny flat in the garden for elderly relatives.
We can also make these a much quicker option, by allowing wooden buildings now that there is much better fireproofed materials available. We could even have an industry set up to produce prebuilt modular housing of some form, I open to suggestions on this??
Essentially we have a housing crisis and we need to make it much easier and more affordable for people to solve their own housing solutions, which a lot more people would do if more land was available at a reasonable cost (within reason, of course), where planning is much more user friendly 
