Step 1: Draw A Selection Around The Main Subject Of Your Photo

In order to create our pop art effect, we need the subject of our image to be separated from its background and placed on its own layer above the Background layer, which means we need to first select the main subject.

You can use any selection tool you want here because you don't have to be overly precise with your selection, since we're going to be removing most of the details from the image anyway. I used the Lasso tool, but if you prefer the Pen tool, for example, that works too. Go ahead and draw a selection around the main subject of your photo:

Step 2: Copy The Main Subject Onto A New Layer

With the main subject of your photo selected, use the keyboard shortcut Ctrl+Alt+J (Win) / Command+Option+J (Mac) to copy the selection onto its own layer. Adding that Alt/Option key into the keyboard shortcut tells Photoshop to first give us the New Layer dialog box so that we can name our layer before it's created:

I named my new layer "threshold", and we'll see why in just a moment. Click OK when you're done, and Photoshop copies your selection onto a new layer above the Background layer: