NOTE: you'll have to go through the Indigo Quarry to get to the Glass Desert. The video doesn't show me taking the normal path to the Indigo Quarry. Instead, I use a teleporter that takes me to a cave that is located near the beginning of the Indigo Quarry.
I've recorded a video showing how to get to the Glass Desert, that I will try to get into this solution.
The teleport that I use in the video isn't necessary, it's just for getting there faster. The place the teleporter takes me to, is the Indigo Quarry.
Added by Flatline 1775: you don't have to go through the Indigo Quarry to get to the Ancient Ruins, you can also get there by going through the Moss Blanket. Going through the Indigo Quarry is the way I prefer, though. Also, you'll probably need at least 2 slime keys, in order to get to the Glass Desert.