tldr; You are not as good at hiring as you think and more than likely will never get any better at hiring so you should use triplebyte.com, interviewing.io, or The Recurse Center. If giants like Google and Microsoft get it wrong with an entire army of statisticians and HR people to sift through the data what hope do you have of getting it right? Seriously, just use one of those three companies and save all those hours for running your actual business.
The long version is that there is a slew of subconscious human biases and heuristics that will thwart all your hiring efforts. This is unavoidable and is a result of how the brain is structured. It is hard to escape millions of years of social evolution. Nature has optimized certain neural pathways and you won’t get around the subconscious heuristics those pathways are designed for. Point of fact, it is more important for people to be in agreement with their social group than it is to seek the actual truth and that’s just the tip of the iceberg when it comes to how your brain is constantly getting in the way of all sorts of things.
The other reason, if I’m being honest, is that you are not qualified to judge the candidates that you will be interviewing. More than likely those candidates will have different life experiences, come from a different social and cultural backgrounds, and in some ways might even be overqualified for the job. Some of them will even be more qualified to do your job than yourself but, again, a whole host of psychological heuristics will kick in and prevent you from seeing that truth. Speaking from my own personal experiences, I have a graduate degree in pure mathematics, I’ve written ray tracing simulation software for fields of heliostats, custom orchestration tools and deployment pipelines for 1000+ node VM clusters, integer programs for optimizing allocation of AWS spot instances, basic evented services that have handled more than 500k events per hour on a single VM, and a few more things. Not once has anyone interviewing me been qualified to understand any of it. That sounds like bragging and it kinda is but you’ll need to forgive me because I’m human and I like feeling special but guess what, those candidates you are interviewing are also like me but in entirely different ways and you are just as unqualified to judge them.
In conclusion, there is no proper way to do technical interviews and you are unlikely to come up with some magical formula that will work so save yourself the hassle and just use triplebyte.com, interviewing.io, or The Recurse Center.