Saving my own work as a block

It depends what you mean by 'coding' and also what you mean by 'my work'

Reaktor makes it possible for folk with little or no coding background to build synths and effects, but it really depends what you are trying to do. If it's really advanced DSP you want to do, that might be difficult without some studying.

No, there is a general specification for Blocks, one requirement is that the main process should be in a core cell.

I think it's reasonable to break this rule in situations where it's impossible or impractical, but in most situations the processing should be done in core.

That doesn't mean you can't build one though. 'Core skills' are pretty much the same as 'Primary skills'. There are some differences, but it's not inherently more difficult. There are library components for oscillators and filters that you can just wire together just like in primary... except they sound better. The one tricky part with Blocks is how the GUI system works. That will take some study, but again once you understand the basics, it's mostly a case of wiring up ready made macros.

You definitely cannot just make an ensemble and 'save as Block' though :)

David from toybox (@bolabo)did some youtube streaming a while back where he created a simple Block from scratch. Definitely worth watching if it's still available. It will give you some idea of what to learn.