In person, or for a remote job, with screensharing and online chats. In my current job, it generally starts with the implementer reaching out and saying, I want to achieve xyz and think about doing abc. That's how the conversation gets started. Granted, sometimes you need code examples already ready-made to gather meaningful feedback, but that can be personal branch, one-off patch, gist, WIP PR ... feedback can happen over slack, simple chat, comments on the WIP PR ... As long as the final ready-for-review PR doesn't catch the reviewers off guard in terms of overal design/approach.