I did a search of the internet for tutorials and patterns on making slips/petty skirts, I came up with "FIVE" really good tutorials and one free pattern.
1. Design & Style: DIY | How to Make Your Own Extender Slip
She uses a preexisting Blah slip and shows how to make it cute by adding wide trim.
|Photo from Design & Style|
2. See Kate Sew: the short dress fixer slip
This one uses a cheap slip from a discount store and sews ruffle fabric onto it.
|Photo from See Kate Sew|
3. iCandy Handmade: (tutorial) extender slip
This crafter uses "Thrift store granny slips" as the base, then adds trim.
|Photo from iCandy Handmade|
4. Trendy Trinket: Pettiskirt Tutorial
This gal shows how to make it all from scratch using lace, trimmings and fabrics.
|Photo from Trendy Trinket|
5. SEW CRAFTFUL: Free Slip Pattern
A 1969 free slip pattern
|Photo from SEW CRAFTFUL|