3D - 3D effect

Enter free transform again (Ctrl/Cmd+t) Right click and this time select FLIP HORIZONTAL. Drag out the copy to the left. Hold down the shift key to keep the baselines aligned. You may also want to make this side a bit thinner by clicking the left middle square (node) and drag it in a little bit. Create a new layer and make another square and fill it with the same gradient, this time make the lightest color at the bottom left.