You'll need:
A normal (white) flask.
Glassblower Bauble x4
Orb of Transmutation x1
Orb of Alteration x?
You can purchase flasks from a vendor, or just pick them up from the ground.
Use the Glassblower Baubles on the flask to get the 20%, THEN use the Orb of Transmutation/Alterations.
This way you can really get a good flask, without having to use more Baubles if you get a good roll on a 0% quality flask.
Getting Glassblower Baubles
Pick up ALL "superior" flasks and save them until the quality on them adds up to 40%, then vendor them together. You will get a bauble for that.
You can also get a bauble off of a single flask of 20%. (unID or white)
Just something I found useful, thought I'd share.
Here's all of the flasks in game: Flask - Path of Exile Wiki