Once all your pixels are soldered and solid, it's time for some gluing and sewing. We'll glue some ribbons to the outside of each NeoPixel strip, to disguise whether they're facing up or down. Then we'll glue the pixels to the corset, and sew some double fold quilt bias tape to the top and bottom edge of the corset to hide all the wires and solder joints.
Hardly anything sticks to silicone. You'll need specialty silicone glue to make this work. Even with silicone glue, some types of ribbon don't want to stick! I found that satin ribbon worked fine, while velvet ribbon just wants to keep separating. Test your ribbon to be sure it's compatible with the glue you're using.
My favorite silicone glue is Devcon Silicone Adhesive. For this project I used Loctite Silicone Sealant, since I couldn't find the Devcon locally and I didn't want to wait for delivery. It worked pretty well, but I still prefer the Devcon -- I think it would have worked better on the velvet ribbon.
Lay out all your strips on the table, making sure all the lights are facing in the direction you want. Tape them to the table so they don't move. Glue a ribbon onto each strip, leaving a little extra at both ends to be sure all the LEDs are covered.
Once the ribbons are dry, place the strips onto your corset with the ribbon side out. Glue them along the boning lines. It helps to pin them in place through the silicone.
To finish the edges, we'll cover them with double fold bias tape. I got the widest I could find, labeled as quilt binding. Bias tape is made specifically for finishing edges just like this (in fact, your corset probably already has some bias tape sewn along the edges). It's cut on the bias of the fabric (diagonally), meaning it will stretch and go around curves really nicely, and the double-fold means you don't have to hem and press and do a bunch of fiddly sewing work. It's all done for you. Yay, technology!
Open your double fold bias tape and place it along the bottom edge of your corset. Fold the corner in at the center front. Tuck all the wires inside so they're fully hidden by the tape. Stitch carefully between the LED strips.
When you get to the back opening, cut the tape with an extra 1/2" or so and fold it inside before sewing. The wires here will need to stick out of the tape -- it's fine to sew right over them, it won't hurt them. Be sure there's enough wire slack so that your adjusted corset will fit without strain.
Continue on the other side of the bottom, and add bias tape to both sides of the top of the corset as well.
Most corsets have a privacy flap at the back to cover the inside of the laces. This is a perfect spot to put your battery. Hand-sew a pocket from a piece of scrap fabric through just the top layer of the privacy flap, making sure your battery cable reaches.
Once the bias tape is finished, sew or glue your Circuit Playground to the center front of the corset through some of the unused pads.
To cover the Circuit Playground but still leave the buttons accessible, I used a silk carnation from the craft store. Cut off the stem and add some hot glue to the back to keep it from falling apart. To make it fancier, I colored in all the edges of the petals with a sharpie.
Give the flower a center. A clear marble or jewel works great here. I used a black leather laser-cut star left over from my LED spats project. Matchy matchy! Sew the bottom petals of the flower to the Circuit Playground, through the unused pads.
Finish by gluing or sewing the switch to the top of the back of the corset, someplace you can reach (but won't switch the corset off accidentally when you lean back).