How did you guys build backlinks?

Here you go mate.

https://github.com/michael-andreuzza/awesome-visibility

We mostly use Google advanced search operators to find backlinks on tier 1 and 2 sites. Like this: https://www.whalepages.com/saas-seo-link-building/

Not a super fast way to build links, but you'll get the best links this way :)

Definitely add your website to every resource listed in the doc created by Michael. That's huge.
Mind that the step above is just the beginning. The next step for you is, like you said, to create content and share it with an audience that will enjoy it.

To create content that attracts backlinks naturally, follow these steps.

1. The way you should think about content is: what can I create that is interesting for both my target audience and for influencers? If you know your market, and I'm sure you do, you can come up with a list of great ideas. Make sure to check websites where your audience is hanging out and write down the most common topics.

2. Create an amazing page with useful content.
   This step is crucial because if the content is not great, nobody will link to it.
   You should really go above and beyond with your content.
   Not only the copy should be really interesting, but the page needs to be beautiful, interactive, fast to load. Deliver a great CX (content experience) at 360 degrees.

3. Reach out. Spend one week reaching out to everybody that might like your article. Post on social media, on private communities, find influencers on Linkedin etc. Make a plan and spend at least 20 hours reaching out to everyone.

Why you should listen to me? My job title is Head of Traffic Growth, my focus is on putting the right content in front of people that need it. The last article my team and I created attracted 12K people in less than 2 weeks, and we work in a B2B market.

Do you have a podcast, or can you appear on one? I've got a great back linking idea :)