A very useful tool that I never knew existed until today. Every mac comes with a utility called “Grab”, in the Applications > Utilities folder.
It’s basically a screenshot application, and it includes a feature for a timed screen grab, under the Capture menu.
It will wait 10 seconds then take a screenshot. You can also use a terminal command:
screencapture -T 10 myscreenshot.jpg
The number 10 is the time delay in seconds, and of course the last input is the desired filename, which is saved in the users directory by defualt.