I made my own slip over two years ago, so I don't have any cool pictures of the process or anything like that, but I can at least give you some basic directions. You'll laugh when you figure out how easy it is, though.
First you will need to decide how long you want your finished slip to be. To avoid making your slip too long or too short, have someone else measure for you while you stand up straight. Since I mostly wear my slip with a dress I measured from my natural waist to below my knee. For me that means 26 inches finished. If you're going to wear it under a skirt you will probably want to start measuring more in your hip region.
I had a straight silky half slip I purchased for $7-$9 from Wal-Mart to use for the top portion. The length you need will depend on your height. I used the top 14 inches of a 24 inch slip. (I am a cheapskate so I didn't actually purchase a new slip. I had one that was needing to be retired so I had no problem cutting it up. You can always save money by making your own top "slip" portion using any basic elastic waisted skirt pattern and some cotton or silky fabric.)
As for eyelet, there are a million different designs. The two main designs usually comes in an all over design or an edge-only design. I used an edge-only design because I wanted the finished scallop portion on the bottom. Since I wanted the extender part to be kind of full, I cut my eyelet to measure 12 inches tall by 72 inches wide (2 yards). (Again, I am cheap, so I used some eyelet that my mother-in-law had given me years ago!)
So, now that everything is figured out, all you do is this:
Cut your eyelet to length and sew the side seems -- right sides together (Mine was 12.5" by 2 yards)
Gather the top edge of your eyelet using a basting stitch
Sew gathered eyelet edge to the bottom portion of slip -- right sides together
Serge to finish off raw edge
Hope this helps. If you have any questions or need some clarifications feel free to ask in the comments or email me.
FYI-Renae sewed her slip directly into the waistband of this skirt rather than making it a separate slip.