shelf brackets for angled wall

I have no doubt this is simple for someone who knows, but...

I was to put shelves on a wall that is slanted out from the floor.  I see Ikea has a locking bracket for shelves but I want to put in bigger shelves than that bracket supports.  How do I make a bracket for this situation?  I am also open to other suggestions.  I want the top shelves to be deeper, say 24", and taper down to narrower depths so I can utilize most of the wall.

Thank you for any assistance.

If the wall runs at a consistent angle you can simply make brackets that attach at an angle, so it tips toward the shelf side you'd be cutting the shape so there's less than 90 degrees between level (the shelf) and the wall or more for it leaning backwards.

If the wall isn't solid, downunder35m's frame suggestion would be good if you want to bear a significant load.

If it is solid, you'll need to to use lag bolts or something similar as opposed to Rawlplugs because there'll be some pull on them whether you put them in level or perpendicular to the wall.

Make a triangular frame for the shelfs.
Front is vertical, back follows the wall.
Add horizontal supports for the shelfs or use a tongue and groove system if you have the tools for it.
This way you have the support you need and can use all the space towards the wall.
There should be no need for a taper as the top of each shelf will sit against the wall anyway - assuming your wall is not leaning to the outside...