Set all units you don't need for defense to one hotkey. Don't use F2 (all units), because you will always need units for defend; I recommend disabling this hotkey (or only use it for last ditch emergency maneuvers.)

Now put Stalkers also on ANOTHER hotkey, so they will walk together and so you can immediately select stalkers to blink. (Sentries' abilities are selected first with your main army, unless you have high Templar in which case you need to put sentries on another hotkey, too).

Consider this midgame example army: Zealot, Stalker, Sentry, High Templar

I recommend these groups:

All (selection will use High Templar) Sentry (so you can use guardian shield or forcefield) Stalker (so you can blink)

(From time to time, make sure your Templars don't walk into the enemy; assign them to a group hotkey if needed. Since you asked for sentries and stalkers to be free, however, you would need a forth hotkey for Templars or use tab once.)

If you want to improve your game in the long run, however, tabbing once is very common (tabbing more, as you said, is asking for trouble); you can train your muscle memory for that on custom maps like "unit tester". This enables you to only use 2 Group hotkeys (1,2) and for the very endgame additionally put Colossi on 2 instead of sentry (with 3 stalkers).

Most also rely on their mouse work to select stalkers manually to blink (ctrl + click); or you can use a tab-once + forth-hotkey-layout.

Lategame example Army: Zealot, Stalker, Sentry, High Templar, Collosi

ALL (use tab to select sentries) Templars (let them walk back and spreading) Colossi (evade focus fire very fast, sneaky vikings, etc) Stalker (instead of 4 you can use R or T for example; 4 is usually bound to production...)

This is not difficult, as you can always just use '1' and will not forget anything of your army, just press the other buttons if needed. It's the most way to play the game, I found, if you actually want to play with your units and not just sit around.

By the way: "Darkgrid" puts all army on Space. Interested people should look at his whole layout.