Having been there done that if you want a very minimalistic PC then just look at pictures of an existing one on the web. Count the pals, they're spaced vertically at 1" and the stitching horizontally is 1.5". THat will give you a pretty good idea of how big you need your pattern to be but remember seam allowance.
The first 3 I made I gave away. These were basically plate pockets with some molle on the front and with a webbing + elastic cord to retainment. The fourth and fifth were okay enough that I gave to my wife and buddy. I retrofitted these with side bands using 'broken catch' quick releases.
The 6 was a clone of a PIG that I reverse engineered by going over SKD's posted images along with YT videos but not quite good enough and I gave that one away to said buddy. #7, also a clone of a PIG was the good one that I kept. :)
So order extra material and you wish to go with some basic 500 and 1000d cloth in solid colors before you branch into more pricey camo colors. Ebay can be a source for cast off in camo, they typically have some issue, either the pattern has a glitch in it or the IR coating didn't take or the WP coating didn't take or something but it's good enough for my needs.
Here's an image of one of my PIG clones in process, the size and dimensions may help you out.
And here's the DW in hers when I was checking fit, it's a IIIa soft plate carrier, not really designed for hard plates or load bearing although there are detachable padded covers for the shoulder straps, the left one is off in this image. It was just a basic design I came up with and is a little wide to fit her soft plates that were custom ordered.