Here's a couple of pics of boxes which might help give some ideas, These range from tiny 300x300(red) to 800x600 boxes.

There's no one way which is better than any other so don't stress over it, just be mindful of high and low voltage wire separation along with grounding and you won't have any issues.


Click image for larger version. 

Name:	20171012_114714.jpg 
Views:	465 
Size:	332.8 KB 
ID:	27564 Click image for larger version. 

Name:	IMAG0545.jpg 
Views:	518 
Size:	639.3 KB 
ID:	27561 Click image for larger version. 

Name:	IMAG1065.jpg 
Views:	443 
Size:	390.7 KB 
ID:	27560
Click image for larger version. 

Name:	IMAG0963.jpg 
Views:	469 
Size:	378.4 KB 
ID:	27562 Click image for larger version. 

Name:	IMAG0701.jpg 
Views:	474 
Size:	344.7 KB 
ID:	27563
Click image for larger version. 

Name:	IMAG0942.jpg 
Views:	553 
Size:	367.7 KB 
ID:	27565 Click image for larger version. 

Name:	IMAG0988.jpg 
Views:	447 
Size:	712.1 KB 
ID:	27566