This one is a little less developed than the others because it's the least straightforward of the ship lines, so I'm trying to avoid getting to tangled up in details too early on.
''This fast hull is comprised entirely of compressed energy and has a single external slot. Structure is low, but stealth and speed are very high. This hull requires a great deal of energy to construct and can only be built at a system with a star of type White, Blue or Black Hole," is the lore I had to work with. As usual, I took a little licence while interpreting that to try and imagine how something like this might be built and used by the race that created it.
In trying to imagine the science and engineering of these, I considered the idea that the hull was essentially raw energy contained and manipulated by electromagnetic fields. The pressure of the energy in the confines of its intangible forcefield container emulate the effects of surface tension, creating something that has all the benefits of a solid object, and none of the downsides like inertia.
I also took some inspiration from the few examples of energy structures I've come across in sci-fi, namely forcefields and Green Lantern's projected manifestations.
As with the other concepts I've put up here, the way these actually work would depend on who is creating them. A pure-energy species, with their natural affinity for manipulating raw energies, would likely manifest the ship around themselves using their own essence to shape and control it. Other races tied to the physical world with their matter-based bodies would need some sort of projector. The projector would contain a massive battery to contain the energy that will power the ship and create the structure. It would also contain the powerful magnetic field generators that would shape the energy. From this idea I decided that the core of the ship, including the cockpit and weapon installations would be akin to standard constructed parts and that the energy hull would form around it when "turned on". Energy would constantly be expended by the processes and some would inevitably leak out, so there is a need to regularly recharge the battery by harvesting energy from stars, but if for some reason that is not possible, the hull-projection can be deactivated leaving the core in a low-power, life-raft mode that will keep the pilot alive and allow for short-range travel.
Where I'll likely go from here is in refining exactly what shape the projected hull might take and how the surface of it would look.