The layout of the New Contacts Preview from Google seems to have hidden some features. As the roll-out seems to be expanding to more consumer accounts, I have seen an increase in inquiries regarding selecting contacts: specifically how to Select All.
Its an easy thing to miss, but its also a Palm-To-Forehead moment for many. This can be done right from the main contacts screen or from a search result. In order to Select All quickly, you select one contact by clicking on the profile picture on the left. Once you select one, you will see 1 selected in the blue bar at the top. Next to the 1 selected is a drop down arrow, click on that and you are provided with an option to Select All or Select None. The latter will deselect any contacts that have been selected. See below for how this appears on the screen.