As a fellow-sufferer of attention deficit, I am the same way. Once I've mapped out a solution, I mentally checkout and procrastinate on doing the actual implementation. One thing that's helped me is by practicing "Deep Work" by absolutely resisting any urge to check my phone during that 45 minute focus time (like pomodoro technique).

Last month, I prototyped a desktop app of a blinking border to assist with getting into a "flow state", which has been pretty effective in keeping me focused for set durations for the past few weeks. Shared with a few friends who have also said it's helped them be more productive so happy to share these tools with fellow HN'ers.

Email in my bio if you wanna give it a try before I launch it on App Store in the coming weeks.