The only thing a Flemish string board does is help you measure the strings without walking up and down your workbench between two nails. It's for convenience's sake alone.
String boards can be set up in different ways. Is the center measuring peg set up for finished string length, AMO length, bow length...? If you don't know, or if it is inaccurate, then you can get results different than what you expect.
The boards do help stagger the strings so you get a taper but that's only for looks, it doesn't add to the function of the string. It's pretty easy to do that if the strings are cut in another manner anyway.
Personally, I like the compact board I use. It reminds me of the good friend and mentor who gave it to me and I can sit in one spot to measure out my strings. But if I don't have a board handy it's sure not going to stop me from making a string.
Guy