Do a Freeform Crop (Not Proportional)?

Start by clicking on the Crop Overlay tool (R) in the toolbar right below the Histogram panel (in the Develop module’s right side Panels area). Then, in the tool options that appear, click on the gold lock icon (in the top right) to unlock the feature that keeps the current ratio in place, and now you can drag each side individually, instead of it all moving at once from each side (proportionally). Once you’ve unlocked the aspect ratio, you can also just grab the Crop Frame tool (in the top left; it looks like an angle ruler) and click-and-drag it out over your image in the shape you’d like (don’t let it throw you that there’s already a cropping border in place the moment you engage the Crop Overlay tool—just click-and-drag on your image like it wasn’t even there and it will update immediately).