To construct a Spy Pengling, you must first have a Scanner tool, which you will acquire the blueprint for when you interact with the Fabricator on your Drop Pod, shortly after the beginning of the game. This guide describes the absolute essentials for building the Spy Pengling, but there are other intermediary tools and equipment that may significantly help you on your way in between each step.
Making the ScannerThe scanner requires a Battery and 1 Titanium. The battery can be crafted at the Fabricator from 2 Ribbon Plants and a Copper Ore. Copper Ore can be found in Limestone Outcrops on the sea floor (particularly in caves) around your Drop Pod and many other close-to-the-surface areas. Ribbon Plants can be found in caves in similar areas. Titanium can be found in many places, often in rock outcrops (any of them) or by scanning a fragment for a device you already have the blueprint for.
Finding the Spy Pengling BlueprintYou can find the Spy Pengling blueprint by using the Scanner at the Phi Robotics Center. You will find a map indicating the center's location at the Delta Station Outpost, as directed by the story. Phi is this symbol on the map: Φ. Or you can head roughly west-southwest from the Drop Pod - a HUD beacon for the Phi Robotics Center should appear when you get close. Keep an eye out for the eyeball jellyfish and you're in the right area.
You will find a wrecked Spy Pengling on one of the tables inside the Phi Robotics Center (next to the bedroom of someone important to your character, more details in the spoiler below). Use the Scanner on it to obtain the blueprint. (There is also another one outside on your way in, but its location is harder to describe due to fewer landmarks.)
Building the Spy PenglingThe Spy Pengling requires 2 Titanium, a Wiring Kit, 1 Silicone Rubber, and a Battery to construct. Instructions for the Titanium and Battery are above in the
Making the Scanner section. A Wiring Kit requires 2 Silver Ore, which you can find (sometimes) in Argentite Outcrops, usually in caves at depths around and below 50m, in the kelp-y area south-southwest of your Drop Pod (look out for tall undulating columns of green-ish kelp, with glowing red pods part way up). Silicone Rubber is made from a Creepvine Seed Cluster, which are those glowing red pods in the kelp! You can grab the seed pods by swimming up to them, no tools required.
Bring all of the materials to a Fabricator (like the one in your Drop Pod) and construct the Spy Pengling. (You will need to transform some of your raw materials into intermediary ones to actually construct the Spy Pengling, such as the Creepvine Seed Cluster into Silicone Rubber. The in-game menus should guide you through the sequence.) The achievement should unlock immediately once the Spy Pengling is added to your inventory.