HMS Glorious pre-war. Note DCT's, 4.7" guns, makeshift appearance and large island / funnel. © Andrew Arthur

Both ships were completed originally as Large Light Cruisers mounting 2 twin 15 inch guns. When these ships were found to be inadequate and there was a need for fast carriers, both were converted along the same lines as Furious;
First, everything above deck level was razed, and a half length lower hangar was added aft, below a full length upper hangar. This hangar led straight onto a small flying-off deck on the forecastle, but this was soon blanked off. An innovation was the addition of two catapults on the upper 3/4 length flight deck; actually to launch seaplanes but late adapted for 'land' planes. A squat island structure was dominated by a large funnel, and there was a small, open bridge and various signal bridges below and ahead of this.
Their armament was also very forward thinking; only along AA lines, and four powerful batteries of four 4.7" AA guns were provided, each with it's own director.
Like Hermes, the heavy island / funnel was not part of the original design, so without trimming, they had a pronounced starboard list. This was counteracted by filling the port bulge with seawater, but to retain the protective quality of the bulge, the fuel in the starboard bunkers was used first, and the bulge gradually emptied.
In 1934/6, three multiple pom-poms were added, one on each side of the forecastle and one abaft the island. In addition, Glorious had the small quarterdeck raised to upper deck level, and the flight deck extended over. With a tripod mast fitted in Courageous, it was now fairly simple to tell the sisters apart.
This pair of carriers were the best conversion for the RN, having the strongest AA armament and air group, yet were lost to the two forms of enemy not designed to combat; the submarine and the battleship.

The eight 15 inch guns removed from these ships were eventually mounted in the battleship Vanguard.