Step 1: Layout of the Main Part of the Cap
1. Measure around your head where you want the cap's bottom to be. Write this down somewhere you can get to it later because if you ever want to make more hats you'll appreciate not having to remeasure. For my hats I normally create one strip of fabric 23" long by 5.5" tall (I wear a size Small-Medium hat normally).
2. Using a ruler and a marker or pencil mark your cutting lines on the fabric
3. Cut out the strip(s) of fabric (in my case I made 3 pieces: two 10"x5.5" and one 4"x5.5" but normally I would only make one 23"x5.5" strip)
Step 2: Sew the Top Band Together
If you're following what I did and using three pieces of fabric you'll get what's in the photos below, otherwise you'll have only one stitched area that will be the back of your hat.
Step 3: Finish the Bottom Edge of the Hat
I fold and pin approximately 1" of the bottom of the band of fabric and then sew it twice; once around the upper part of the fold and once around the lower part of the fold. This gives a nice double stitch that looks good.
Step 4: Make the Top of the Hat
Cut out the circle of fabric.
Step 5: Pin and Sew the Top to the Hat-band
I've had best results by starting with a pin at the back and then pinning the front and then each side followed by a pin in between each location. For me this ensures that the pinning is even all the way around.
Sew the top on and flip the hat back right-side-out and try it on. Hopefully if everything has gone ok it will fit exactly where you want
Step 6: Make a Brim (the Threadbanger Way)
After cutting out the shape I covered both sides in duct tape and then traced out and cut two pieces of fabric 1/2" larger than the brim. When cutting out the fabric make sure to cut straight across the back edge (don't follow the inner curvature of the brim pattern).
Pin and sew the two pieces of fabric together along the curved front edge and flip it around so the stitches are inside of what is now a pocket.
Place the paper brim inside the pocket and pin and sew along the back curve of the brim making sure that the fabric is pulled tight from front to back before pinning.
Step 7: Sew on the Brim
The bottom edge of the hat-band should follow exactly along the sewed back curvature edge of the brim.
After sewing I cut the extra fabric off of the brim pocket so that it doesn't interfere with how the hat fits (though you could also leave it if you like).
That's it! If you're really feeling confident you can try to create a liner, but I don't like my hat to get too hot so I tend to leave that out. Thanks for reading and I hope this helps someone!