I'm not 100% certain of the nuances of the method, but if it's regularly employable it should be a great asset to maps as we move forward, enabling maps like Electric Circuit or Monty Hall in SC2.
Down to it:
Please note: The position of the Geyser and Minerals relative to each other, and the fact that the Geyser and Minerals that get glitched through are owned by the active player. This is important--If the geyser/minerals are neutral or hostile this glitch will not work. So for 2-4 players maps, repeat the formation for each player. Don't worry--They don't grant vision.
This is the formation that allows workers to be glitched through as they build. When a probe stands in the circled area and builds a building, such as a Pylon over itself, it will be pushed through the very small crack between the Mineral and the Vespene Geyser. Similarly, an SCV placed there needs to build a Depot over itself, then you spam T until it slides out.
Looks like so:
Of course the method to do it with a Drone is a bit more complicated but it still seems to work: With the Drone positioned in the red circle, spam click it to the unpathable spot JUST beyond the minerals. There's one little area where you can click and the Drone tries to walk through the Geyser but fails. That's the spot you want to spam on.
Next, bring another unit (I used a Queen) to spam the same spot. Eventually, it's animation will glitch slightly and it'll look like it's in slow motion. Build an extractor, and then immediately continue spamming with the other unit. Cancel the extractor and if done right, the unit will push the Drone onto the Geyser, and it can be walked across.
I've only tested this formation but there may be others.