* Set up "office hours" where coworkers can come and ask you questions. Even if you don't actually have an office, this is just a set period of time that you've blocked off for people to visit you at your desk and receive assistance.
* Turn off notifications on Slack, e-mail, etc., and only check those things periodically throughout the day. If you're cruising on some new feature, don't switch over to Outlook. Keep cruising.
* Don't be afraid to say "sorry, I'm in the middle of working on this thing -- I will follow up with you later." You are the only protector of your time. Everyone else will steal as much as you allow them to steal.
* Wear headphones. People are less likely to interrupt when you wear them.