Step 2 Use the Polygonal Lasso tool (L) to separate the subject from the background in the duplicated layer. This can be done quite roughly. Once the subject is selected, go back to the original layer, invert your selection (Cmd/Ctrl + Shift + I) and delete the background. Now you can delete the duplicated layer.
Step 3 Now choose the Crop tool (C) and select just the subject’s face and a bit of her chest. Set the Crop Guide Overlay to None in the Options bar to help you see what you’re doing. For now, we’ll keep the image’s resolution unchanged.
Step 4 Duplicate the layer, name it ‘Contrast’, then increase the contrast on this layer. Duplicate this layer and select Image > Adjustments > Posterize with a Level of 4. Now rename this layer ‘Posterize’.