We are turning an upstairs bedroom closet into a wardrobe. I have fitted two clothes rails and hoping to get some melamine white shelving done. The walls are far from even. The shelves are to be 820mm wide and and 675mm deep. But having measured the width at the front of the shelf, it’s 820mm but at the back wall it’s 790mm. So good bit out. I’m no joiner but hoping to tackle this myself as it’s an upstairs closet it doesn’t have to be perfect but would like to get it best I can Any tips on scribing this to fit.