One advantage of a vertical blind is that that the slats secure to the headrail at the top but do no secure to anything at the bottom. This means that when you mount a vertical blind on an angle, the head rail will remain at that specific angle but the slats will "self-adjust" and hang straight up and down over the window. This allows you to follow the contour of an oddly shaped window but still supply adequate shade for blocking sunlight and providing privacy.
Things You'll Need
Attach the blind slats to the headrail if they are not already attached. Slide the end of the slat with the hole in it into the plastic retaining clip. You know the slat is attached properly when the end of the clip is centered in the hole on the slat. Usually you would install the slats last, but in this case, since you plan to install the headrail at an angle, install the slats first.
Place the headrail over the window frame and center it. Raise or lower one end until you achieve the angle you want. Check the bottom of the slats where they rest closest to the floor. Keep the slat at the lowest point of the angle at least 1 inch off the floor to allow for clearance. As you move to the highest point of the angle, the slats will progressively rest farther away from the floor.
Mark the ends of the headrail on the wall with a pencil and scribe a line along the top edge of the headrail onto the wall. These lines will help you when placing the mounting brackets.
Place the headrail off to the side and then place the mounting brackets onto the wall. Line the brackets up against the lines you scribed onto the wall.
Mark each mounting hole onto the wall for the brackets and drill holes large enough for your wall anchors.
Drive the wall anchors into the holes with a hammer and secure the brackets to the wall anchors with the supplied screws and a screwdriver.
Attach the headrail to the brackets. This process differs. In some cases, you must attach the headrail with screws that go straight through the front of the headrail. In other cases, bend a tab on the bracket and force it into a slot on the bottom edge of the rail.