Onboarding is different. The work you would put into onboarding directly, you mostly put into documentation and architecture so people can achieve goals without having to have a mental model of the whole application. Try to design your application so you can part out components/endpoints/modules to people on Fiverr - you code is decoupled and documented well enough that short term contractors can come on, look at an example/template and fill in the blanks for the current requirements without a ton of direct support. When you're at that level, onboarding basically reduces mostly to a quick task overview/ticket discussion, a few DMs over slack and a code review.