So many good advice you've already got
My dogs have never had alone problems,
although they always follow /are with me all the time when I'm home
They are never put away - never been in cages inside (never owned one)
That way they learn what's right and what's not
so good
It is important to me that they learn to have
full confidence in me
Now to the case

When I get ready to go - Minnie also gets ready

I say 2-3 times along the way - "no you have to stay home" with
a soft confident voice.
Just before I go out, I spread a bit of Minnie's food around the living room floor
- says "mom comes in a while" - out and lock the door in a hurry.
Everything very "not pedagogical" - but it has worked for us.
But now Minnie is also smart and understands everything I say.
Think it's very important to be very confident - and believe in the project.