I used EquityZen a few times to sell shares and had a good experience with them. The main things I'd do differently are probably not hire a lawyer or at least find one I knew specialized in startups (I had the first deal with a lawyer and subsequent without and it just seemed to add friction without value, but who knows...I'm not a lawyer haha) and learn about Qualified Small Business Stock (QSBS) for tax purposes/talk to accountant that specialized in startups. The accountant I did talk to (recommended by my lawyer :-p) didn't mention this at all even though it did qualify.
The deals did need board approval, but it seemed like it was more to determine whether they wanted to exercise the right of first refusal (they did in the first deal and did not in subsequent), but maybe standard terms have changed since the rise of secondary market platforms. It was a bit nerve-wracking the first time since I didn't know what I was doing and I was most likely the first person to do it at the company, but it ended up working out fine (probably also worth noting I was no longer an employee at the time of the deals). Good luck!
The deals did need board approval, but it seemed like it was more to determine whether they wanted to exercise the right of first refusal (they did in the first deal and did not in subsequent), but maybe standard terms have changed since the rise of secondary market platforms. It was a bit nerve-wracking the first time since I didn't know what I was doing and I was most likely the first person to do it at the company, but it ended up working out fine (probably also worth noting I was no longer an employee at the time of the deals). Good luck!