My observation is that code reviews are one of the worse solutions to the problem. They are almost never done right. People tend to treat them as nuisance and not focus or focus on the wrong things. Or people try to be nice to other people and "not make problems". They are constant source of problems because they tend to crash into deadlines and usually lose. It is also frequently the first time somebody finds out somebody else spend a week writing a feature producing completely unusable mess which could have been avoided if there was human contact during development. Also reviewing large body of work after it has been "completed" is simply the worst time to have open and critical discussion about quality.

My tested and recommended process is working in pairs, rotating pairs regularly and sharing/rotating all tasks within pairs, equally. You have two people actively working together on each piece of code. They are supposed to both understand what is happening, care for quality and be vigilant to catch defects. This is also the right time to have actual input regarding quality or design improvements. And the code once it is done can immediately be committed and shipped so there is no awkward delay between code finished and deployment.

I also learned over the years pair programming is also a fantastic way to achieve some other goals like people socialising, getting to know each other professionally, learning from each other, newcomers getting bootstrapped, etc.