Pick an app, choose how long to wait, and put the shortcut on your home screen. Tapping it shows a blank screen for the seconds you chose, then opens the app.
Most habits on a phone are not decisions. The hand moves, the app opens, and a few minutes are gone before anything was chosen. Blockers answer this with a wall, and a wall invites a workaround.
SlowLock does one thing instead: it puts a few empty seconds where the reflex used to be. Nothing is forbidden. If you still want the app after the wait, it opens. Often you will have already put the phone down.
The app makes no network calls, and you can check that yourself. Read the source, build it, or file an issue.