Cut the feature list before you build it
When you build alone, the bottleneck is always you. There is no second engineer to parallelize with, no team to absorb scope. The only lever that actually moves your ship date is how much you decide not to build.
So before I write a spec, I write a cut list. Not the features the product could have. The features this version will not have, on purpose, so the one thing it is testing can ship this week.
The one bet
Every early product is really testing a single bet. Will people pay to chase overdue invoices automatically. Will a branded intake link save someone an afternoon of setup. Everything that does not directly test that bet is a candidate to cut: the settings page, the second integration, the onboarding tour, the dark mode.
You can always add them later, after the bet pays off. You cannot get back the weeks you spent building them before you knew whether anyone wanted the thing at all.
Ship small, learn fast
The smallest thing that honestly tests the bet beats the polished thing that ships a month late. A rough version in front of real users teaches you more than another week of features in private. Build less, ship sooner, and let what you learn decide what to build next.