Friction before Timesink apps
A short pause and a confirmation before opening anything you've flagged as distracting — enough to break the reach-and-tap reflex.
Hidden from search, by default
Apps you've flagged as Timesink don't show up when you search the drawer for them. If you really want one, you have to go find it.
Notifications can't be a shortcut around it
Optionally suppress notifications from Timesink apps entirely, so there's nothing to tap that would skip the friction above.
Groups
Group any apps together — Social, Work, Games — and they fold into a single line in the drawer. Fewer names to scroll past. Make a whole group Timesink, or give it quiet hours so it stays shut while you work.
A plain home screen
Today's date and your next few calendar events. That's the whole home screen. Nothing else competes for a look.