Cut your fabric according to the pattern (you'll have 1 piece for the apron top, 1 for the apron bottom and 2 for belt)
Cut the interfacing 1/8" narrower than the belt then fuse to the belt.
Sew both strips of fabric for the belt, with the wrong side out, all the way around, except for about 6". Turn the belt right side out through the opening and gently push the corners out with a poking tool that's not too sharp. I admit this was a bit tricky and required some time for me to get it right. Close the opening with an edge stitch then steam iron the belt.
Take a super long strip of fabric (about 20 feet long and 2 1/2" wide) and ruffle it using your machine settings to make ruffles. If you use a Singer 1507WC which is an awesome machine for beginners, use a stitch length 4 and a thread tension at 6. Or you can go the easy way and use a ruffling foot, which will get you beautiful, even ruffles in one go.
The ruffled fabric should be enough to go around the top and the bottom piece of the apron, minus the part where these join the belt.
Take your apron top piece, place it right side out and match with the ruffled fabric as below. Pin and sew. About 1/4" away from where you stopped sewing, cut the excess ruffled strip and use it for the bottom piece.
Make the straps as wide and long as you want. I made mine about 1/4" wide and 10" long. I folded the fabric in half, then I folded each half, then folded again where I first started to fold, then sewing on the open side of the strap. Then I knotted one end.
Decide where you want the attach the straps and make marks then attach the straps with a pin.
Open the bias tape and place it on top of the ruffles, with one of the folds matching the stitch where you joined the apron piece and the ruffles.
Pin in place and stitch all the way around that fold mark, making sure to remove the pin who keeps the strap attached.
Then fold the bias tape over to the back of the apron piece (wrong side), pin and stitch with a 1/8" seam from the open edge of the bias tape.
Do the above steps for the bottom piece of the apron (except for the straps part).
Take the bottom piece and ruffle about 12" of its top edge.
Join the bottom piece and the belt, right sides together, pin at the top and stitch; make sure to catch a bit of the ruffle.
Fold the belt out, facing you with the right side. Place the top piece of the apron, wrong side out. Pin and stitch, making sure to catch a bit of the ruffle too.
Finish the belt seams on the inside of the apron with bias tape as above. Or serge or do a zig zag stitch. If you use bias tape, make sure to fold the ends in.