I make 3D printed street signs for coworkers but I have to split the models to fit on my A1 build plate so I was joining them with galvanized angle iron which costs about $22 for a 4 foot piece. To save money, I made some angle brackets to print in PETG, but you can can use PLA for faster printing. Printing Generic PETG takes about an hour for the two main pieces but only 45 minutes with a Bambu PLA/PETG print profile

The model is split to fit on an A1 Mini for a combined length of about 360mm. The second plate is an extension that you can print to add another 160mm, multiple times if needed, theoretically to infinity!

I attach them to my models with Plastic Bonder (JB Weld) but CA will likely work for light duty adhesion. 

No support needed for the holes in included orientation. 5 walls for strength on 0.4mm nozzle.