Arranging your own insurance is not particularly difficult for old style apatrement blocks.
It gets trickier for the multi story blocks now prevalent.
I’d suggest using a broker. They are remunerated ( of course) by either a fee for service or by commission from the insurer ( but not both).
You can negotiate a deal with the broker.
Brokers often have access to insurers not available to Joe average ( because some insurance companies don’t want to deal with Joe average.)