First, please note that the majority of my tabletop design experience is in compatible products for larger RPGs such as Pathfinder, but I do have some strict “board game” experience as well.
With board game design and developing I think a good starting is to iterate on a set of simple rules until you have a basic cycle of play that flows well. I realize this is a big task and it’s hard to know where to start. Teaching this process would probably be multiple classes by itself, but you could check out Board Game Design Lab for some resources. Personally, I tend to make a prototype on simple physical material (cardboard, simple tokens, etc…) without visuals. This helps isolate core gameplay. When you have a basic game without a theme that others can understand and play easily then you have a good start.
If instead you have a thematic idea as to start then develop whatever ideas you’re excited about. Ultimately, though, you’ll need to be able to communicate that narrative through simple gameplay. In my opinion, even the most complicated board games most often have simple ways of delivering narrative once you’re playing (backstory aside…). Simple decisions in gameplay: singular die roll or card draw have huge story implications when playing a board game that has a strong narrative. That’s why I think it’s really important to have a clean and simple play experience.
You have also developed your own games already, so feel free to let me know if you feel different.
Crowdsource funding is still viable for board games to a degree (Indiegogo, Kickstarter, etc…) but pretty tough to get enough interest. Joining online communities and showing genuine interest in other people’s work can really help in my experience. It’s also a lot of work. I do know of some projects that have had success with local distribution only at start and THEN hired a publisher to widen distribution. I can’t say I’m very educated on that approach, however.
Hope this is helpful… I’m not a professional, but have designed several tabletop products and had some moderate success Others may have different input and perhaps more experience.