Step 1: Materials and tools
Mitre saw is really usefull, though a fretsaw might be enough. Fretsaw is a must due to round cuts.
Step 2: Construction points and blueprints
About the blueprints - it's made to print on 8 sheets of A4 paper. Once you print those, glue/tape them together. To aid in the process, there are letter A1BCDE.... to mark the cover and overlap. Put two sheets on the glass against your window and you should match the overlap perfectly.
The blueprint only covers the top, two rounded sides, "holder", as the rest is pretty simple 5x10 cm straight cuts.
For the small decoration (P form like) pieces and the top "spike" pieces, I drilled two holes in each. Wooden sticks then go into each one to hold them together. Use some glue to make it permanent.
Step 3: Sides
Used some natural water-resistant wood to make the sides last longer.
Step 4: Wooden arbor - finished look
This is how it looks in the end. Bit of paint still missing.
I'd say a nice weekend project. Did cost me around $100 for lumber, paint, concrete