Break out the table saw, and dial in a 45 degree bevel! I ripped some left over spar waste to generate 45 degree bevel stock so that I'd have better surface area to glue and staple the slanted front wall to. Not sure how well this pic shows it; but that's a 45 deg beveled piece glued and stapled to a spar that is perpendicular to the plywood surface. I did this both for the top and the bottom of the wall.