How to make a scratch disk

First you go to final cut pro, system setting

create new folder in HD2 then by going into system setting you can choice the folder that you want to save your work

You autosave by setting the folder you want to save your work and save automatically

by clicking cmd+Alt 1,2,3 it change the selection colouralso you can rename the folder by clicking right click

By right clicking and selecting new bin that will allow you to create new folder where you can put some video or images inside it and name it.