as you can see in the image, suberu becomes suberiyasui for the “easy to [verb]” grammar point
however i don’t understand how come the ru/ri didn’t get dropped as it’s a verb that ends on “eru”
like taberu → tabeyasui
or 汚れる → 汚れやすい
what’s going on?
That’s because 滑る is an いる／える exception. IOW, it’s a Godan Verb. I made a post about this not too long ago, where I have a list of all the いる／える exceptions. There’s both a simple list in an image from Tokini Andy (which will probably be enough at first) and also a more in depth one with pretty much all of the exceptions listed. Here’s the link to that post:
HTH!
oh that’s it. i forgot about the exceptions haha
thank you very much for your response and the post you created. I’ve bookmarked it for future reference 
