My second DIY pedal, easy to build and sounds really nice. The LEDs light up when signal passes through them so I mounted them on the outside of the enclosure. Some notes about the layout:

* Found a lot of conflicting info about diode orientation and actually ended up building two versions. First I followed the schematics from Fuzzdog and Moonn, and it sounded good but the LED did not light up and removing it had no noticeable impact on the sound. For v2 I tried flipping the LED and one of the 1N4148, like in the layouts on Tagboardeffects and Effectslayouts and some other schematics floating around online. In this version (the layout in this post), the LED does light up when playing. Still not sure if I made some kind of mistake with v1 but at least this version of the circuit seems to work like intended.
* Added an SPDT switch to select between a blue LED and a red LED. The blue sounds more dynamic and is slightly louder, the red sounds more compressed, but it's not a huge difference. The blue LED that I used has 3.3v forward voltage and 1600mcd brightness, and the red is 1.95v and 1300mcd. I would say it's the appropriate brightness range for visible LEDs. Both are diffused.
* The circuit is extremely responsive to pickup selection, guitar tone/volume settings, pick attack, etc, and I read somewhere that the octave effect works best with low output single coils. My guitar has Lace Sensors which are pretty high output, and I don't get the strongest octave effect but other than that it sounds just like the demos on Youtube.
* Could easily fit on a smaller board but I have a bunch of 20x16 boards and they are small enough.

Fuzzhugger Phantom Octave + perfboard layout