A while back we brought on an engineer who gave the cleanest technical interview we'd seen that season: fast reasoning, knew payment flows cold, no bluffing. Three months in they took a week off, and the rest of us couldn't move their work forward. Not because it was bad. Because the only place it was explained was in their head.
We spent days reverse-engineering decisions that would have taken ten minutes to explain, and we had an awkward conversation with a client who only wanted a date.
So we added a last step to our interviews, and it's probably the one we'd suggest you copy. After the technical part, we ask the candidate to hand their solution over: five minutes, explain it to the person who'll own it, as if you're going away tomorrow. We don't re-score the code. We listen for three things: what they chose not to do, where it will break first, and what we should check if it misbehaves on a quiet weekend.
It changed who we hire a little. It changed what we learned about people we were already going to hire a lot. Someone who can hand work over makes the whole team interruptible, and that's the real thing a client buys when they hire a team instead of one person.
It's worth naming the one job on your team you'd want someone else to be able to pick up next week.