After buying an extender slip for thirty dollars from a local boutique, I have been wanting to make one for myself. Being pregnant, this has come in so handy because my dresses keep getting shorter as my stomach grows. I just used a knee length slip I already owned and found some different white and cream lace from JoAnne's. I feel like using the different shades of white help it go with more things. Adding lace to an existing slip is as easy as sewing straight lines, so trust me- if I can do it, anyone can. But there are many tutorials on Pinterest, including this one http://icandyhandmade.blogspot.com/2011/08/tutorial-extender-slip.html
I'm definitely a skirt and dress kind of girl, so this has saved me! Plus, I love the added texture under skirts.