Just some insight as to how hair naturally behaves.
I recently gave up on styling a part into my hair, rather with my current hair, a natural 2:8 ratio forms on the left side, so I now just work product into my hair and toss everything back with my fingers.
This is how my hair looks like this morning (By vilian Blow + Dynamite Clay):
As you can see, there is already a part forming on the left side of my head.
After 30 mins or so, the volume drops and the part becomes more obvious as the hair strands fall down. It's not ideal, since I like my hair to be "poofier" but I live with it. Why? My hair is obvious not long enough, the longest strands only reach the top third of my nose.
So i will just be patient and live with less than ideal hair for the time being.
As to the guy asking for advice, I assume slick back undercut means something like:
You mentioned your hair naturally want to center part. Well, you certainly can manipulate the parameters by blow drying and using product, but judging from what i seen, hair barely past your eyes is no where near enough to do a proper slick back.
Look at the above, his hair is definitely longer than what you have described so far.
My recommendation is to join me in growing those strands out