Thanks for the comments above.
The harder part, founders and would-be founders, is to adjust your process. I'd say 90+% of the requests I see from startups is of the "I have an idea and just want you to implement it" or "just take my slides and make them elegant" or "I know the market" or "we don't have time to research". I've tracked all of the ones who tell me this; all of them fail quickly.
So, in practice, think ahead, and realize user research is a vital part of the design process (where "design"!="how it looks" but "design"=="how it works") if you want to build something people will use. I'll quote a senior design exec: "research is an inevitable part of the process that they will end up paying for anyway, so they might as well be involved in it from the beginning (“it’s going to happen because it’s a fundamental part of the design process, I guarantee you if you think you’ve had designers working for you doing no research you’ve really just had designers lying to you about their research habits and claiming their research insights as their own brilliance.”)"