Ask HN: What makes a good senior frontend coding interview?

My startup is hiring a senior frontend developer, and we’re trying to improve our frontend coding loop. Our current loop is React-based, we give them a view of what their page should look like, test that they can design some semi-complex state to make the page function correctly. We give them 3 hours to solve it, with checkins each hour for them to ask questions and show their progress. It’s a relatively simple app to build, and we let them choose their component library.

But we’re struggling to get good signal. In many cases, the candidate’s code has multiple issues, though it’s often not clear whether they would be able to fix it with a bit more time or if it’s core misunderstandings about how to write good frontend.

We’ve debated making it an unlimited-time takehome, but we worry that this is disrespectful of a candidate’s time. We are sympathetic to candidates who are doing many of these interviews for different companies. We do know that there’s the option to pay candidate’s for their time - but we are still hesitant on doing a takehome for other reasons, for example it’s hard to compare an engineer who takes a full weekend to complete a takehome, versus someone who submits it within an hour.

Additionally, we find some value in the check-ins, to see the candidate’s thought process.

So far, though, we’ve had no luck with the current structure, so we’re looking to refactor it completely.

So my question for HN: how do you structure your frontend loops? What works and what doesn’t work? Any suggestions for a small startup looking to get good signal without taking too much of a candidate’s time?