All parts in the example pictures are printed with a 0.16 mm layer height. Everything should just snap together. The big number 3 has a separate “pixel” on the back of the sign, which may need a drop of glue, just to be sure.
 

⚠ The tiny number 3 has a loose “pixel” which can be hard to place into the sign. Use of tweezers recommended. 

Base: Polymaker PolyTerra PLA - Marble White

Sign: eSUN PLA+ - Black

Numbers: eSUN PLA+ - Orange

 

(Photo by @BasicAppleGuy)

TIP: Also check out the other models:

Apple 1 Infinite Loop Visitors Sign
Apple 2 Infinite Loop Sign