I ended up using a zipper because the bag was too wide and soft to stay closed with just a frog.
Here are the steps involved in lining my clutch:
Step 1: Measuring. For a cuboid bag like mine, follow the steps in jordy's tutorial to make a box shaped lining.
For an envelope bag, just fold a piece of fabric in half and sew up 2 sides to get a flat lining.
Once you have sewn up the lining, fold over the extra one inch and press to get a cuff. The seams should be on the outside at this point.
** Yes, I know I didn't cut out my pattern pieces as in step one, however, do as I say and not as I do because I'm a lazy person.
Your results will be much neater and easier to work with.
With the zipper closed, line up the side seams of the lining with the center of the zipper and the side of the bag.
Repeat on the other side
Then, pin the lining to the zipper and the purse, taking care to line up the distance between the zipper, lining and purse.
Sew along both the long edges of the zipper first, catching only the inner loops of the crochet. Accuracy is not really a big deal here, as long as the stitches do not show through on the other side.
Lastly, tuck your zipper ends in and sew tight. Escape your thread by passing the needle through the crocheted part of the purse. A light tug should transfer the knot to the inside of the crochet. Then, pulling the thread taut, cut it close to the bag and the thread should snap right into the space between crochet and lining.
Stringed musical instrument! You're done.