Not a complex process.
As a rule, tipping is not expected in Slovenia, although as another rule serving staff are rarely well-paid and tend to work long hours in public, standing up, so leaving the change is always welcome, and any more would be nice.
One thing to note: if the attractive server smiles at you this could be part of his or her job, so don’t get too excited and just enjoy what you ordered.
And while you're in the country you might be interested in...
How to spend from 4 to 48 hours in Ljubljana
What's on in Ljubljana this Week
How to spend from 4 to 48 hours in Bled
How to spend from 4 to 48 hours in Piran
Related: What's on in Ljubljana this Week