Print as rotated in the STL-Files, obviously with “Support on Buildplate”
I “glued” the Plates to the window using Tesa Powerstrips (2 for the short and 3 for the long one), holds perfectly for over a year now.
You need a Plate for the Windows and at least one Planter, the long Plate holds 2 big or 3 small planters.
The smaller planter has 60mm diameter at top, the bigger 100mm.
As there's no drainage, please don't put soil directly into these planters.
The author hasn't provided the model origin yet.