To defeat Gleeoks you basically need:

• A good bow
• A way to easily enter bullet time
• A good weapon to attack while it’s down
• Additionally, some elemental defense

For the bow, the Lynel bow is the best, but a Demon’s King bow may do too

To enter bullet time: find somewhere to ascend, or deploy a portable platform (autobuild), or a Hover Stone. The Hover stone can be attached to an arrow, and shot on top of link, and is also a good elemental shield, manipulated with the ultrahand.

While in bullet time, attaching gibdo bones is an effective attack, just aim for the eye on each head. If the gleeok is too far away, an elemental keese eye is a good option.

Have your friends with you, so they can help too.

Just doing that (bullet time, arrow to the eyes, hit it 3 or 4 times while on the ground, ascend and repeat) you’ll be able to defeat any gleeok.

I’m not a good player and I can beat any gleeok in the game that way.

Cheers.