Don't write code. Break down a feature into tasks that you would take 30 mins or less to accomplish. Have them build each task one by one. If they take longer than 1 hour, you know that they are stuck on something so you can go help them. While they are working on 1 task, you are figuring out the next 2 tasks. Your job becomes quick prototyping to make sure the tasks are feasible.

Eventually, after many small merge requests, junior developers will be comfortable to take up entire features. After a few features, you teach them how to break down tasks for other junior devs, just like what you were doing before.

We have been actively following this method for the past 2 years and have taught engineers with 0 coding background all the way to become tech leads in our org.