How do you make a grinder?

The question is: to be or not to be a grinder! -TOTALLY not an edited Shakespear quote

How do you make a grinder, I'm trying to make a NO XP grinder for skeletons that is created using a skeleton spawner and the items can be pumped to other sections of my base. Could someone link me to a video or image about how to make this Thanks if you can, thanks for reading as well! have a good day!