Grab your supplies! A cheap plastic mask from Michael's will do fine (that's what I used). The heat of the hot glue may warp it slightly, but don't worry about that you will be covering it with glitter later.
Once you have all the supplies lay the mask on top of the felt and trace the shape of the mask onto the felt. Cut it out, then hot-glue it to the back of the mask. Be aware that you DO NOT put any hotglue on the area bon the felt where the eye holes will sit, when the glue dries it will be visible and look like crap. I wasn't paying attention and did this. You can fix it - somewhat - by coloring over the dried glue with black sharpie, but it is better if you avoid it completely.
Once the felt has dried onto the back of the mask, squeeze some hotglue onto the front. You will want to cover EVERY inch of the front of the mask, so you can use a paintbrush to spread the paint around. I used my finger which worked out fine as well! When the mask is covered, sprinkle your glitter on top. It works best if you choose a glitter that matches the color of the mask, so that any openings in the glitter blend nicely.
Final Step! Make sure the glue and glitter is somewhat dry so that it's not getting stuck everywhere. Find some decorative accents (I had a hand full of jewels I pulled off an old shirt) and hot glue them onto the mask in whatever way suits you. The best part about this project is that you can create a ton of different masquerade headbands, and no two will ever look the same.
When everything is dry and it looks how you want it, Glue it to the head band and TA-DA! A hair accessory The Phantom of the Opera would be proud of!