Comment by mesotron_dev

Rent a private office. Preferably with 24-hour access. Wifi is a bonus and commonly included. It helps to have dedicated workspaces. A coffee shop could work if it has a good setup for coding & good coffee. Create the space for the project, and then you'll have the time for side projects.

As for design it takes time but being able to dedicate time to the top-down grand scheme and then go bottom-up is crucial for any size project. What are the fundamental requirements? Keep it simple. Deconstruct all aspects into single-purpose functions. One input, one output, & repeat. The ongoing pattern is to change the level of abstraction used for reviewing the project at any range, from a function to the whole project. These reflexes take time to build, and working on a side project daily is an excellent way to discover what patterns work best for your programming style and the project you're working on.

And big project ideas provide a field of side projects to discover. So wade into the water and find some fundamental piece of your larger idea. And then zoom in on that. When you're considering optimizations of compiled code to run a single binary on a static empty container image, you've gone deep enough.