2. You can use whatever measurements you want. The distance from the bottom to where the notch is cut out will be the height of your purse plus seam allowance. I used 1/2" seam allowance, and the height of the purse was about 4", so from the bottom to where the notch is cut was about 5".
3. To figure out the notch measurements, imagine doing a regular Jordy bag
, except that instead of having 2 pieces you are eliminating the bottom seam by turning it into a fold. So when you make that fold, you want the depth of the notch to include a seam allowance. The fold doesn't need a seam allowance. Make sense? I don't remember the exact dimensions of the one I did (I was going by the squares on the fabric and just adding seam allowance), but basically the depth of the notch should be 1/2" (if that's your seam allowance) longer than 1/2 the width of the notch. The idea is that once you sew that side seam, the distance from the stitching to the corner of the notch is equal to the distance from the bottom fold to the corner of the notch. That way you get a square bottom.
I hope that made sense ... it is quite tricky to explain without being able to hold it in your hands.
The flap piece is basically the depth plus the height of the finished purse. It's probably easiest to decide what you want your finished dimensions to be, draw it out, then add a seam allowance around the whole thing.
I made a pdf to show how to draw out the finished dimensions and add the seam allowance. Hopefully this helps clarify things: Boxy Purse PDF
this pdf is not to scale, it's at about 55%.
Good luck! I'd love to see the finished product. Feel free to message me if you are having trouble.