These came out flat - what should I add more of? I also left a comment with more details.

A couple of possibilities: Your butter may be too warm. Your flour measurement may be off. And I just read somewhere recently that silpat liners hold on to cookie dough better than parchment or foil, and give better rise (but I can't find the reference, sorry). Here's an article from David Lebovitz that might help: http://www.davidlebovitz.com/2006/12/why-do-cookies-spread/