Just let the candidate talk about their career and what they have done. Ask their opinion of certain things. Ask about how they tackled certain projects and give them the time to answer and go off on tangents. Treat it like you are a few friends having an in-depth discussion over drinks.
Technical interviews focus too much on headline points. They want the candidate to touch on or mention certain things that everyone should know about the subject. I'm not interested in that, I'm more interested about them mentioning less obvious things such as known quirks, bugs or tricks about the subject matter. Stuff that only a regular user would learn about.
The problem with this approach is that for many companies HR insists on structured interviews. I once had do some interviews for a couple of C# roles. The interview format was literally the same as the game show Talk About. The interviewee was given time to talk about a subject and we had to tick off a list whether they mentioned certain keywords and phrases in the allotted time. The same format applied to the HR interview. Whoever scored highest got the job, a very silly way to do recruitment.