headless install

I am trying my first headless install on a raspberry pi (I have done the monitor/mouse/keyboard plugged in way many times) but I'm stuck. Can I plug the ethernet cable directly to my laptop or are the instructions on the sarpi site expecting that I would plug the pi into a router than access the pi using ssh that way? If I plug the pi directly into my pc (running 64bit slackware current) what do I need to do on the laptop side for the pi to get an ip address? I would appreciate any help just steer me to a bit of documentation, duckduckgo searches all lead to things that start with 'open my network on windows10' with pictures of park benches or use systemctl blah blah.
Thanks