I am think of a lantern consisting of 3 windows. This will create an upright triangle to fit into the required measurement. The windows would be upright not slanted. Each window could have a window box with a flower that slowly goes from bud to bloom to show the passing of time from early spring to Summer. Maybe a rainbow arching above the windows or in the windows themselves. There could be a silhouette of a person inside the triangle of windows.
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Initial design thoughts
I started off in my garden, then realised I wouldn't be able to get through the door, & Pippin was a real distraction. Now moved to workshop near Wivelsfield.