Investors looking to get a jump-start on a stock ahead of a flat-base breakout just might be in luck. But first, let’s review the basic traits of a flat base. These shallow patterns often start forming as a stock takes a breather after an earlier advance. So they’re more likely to occur as a second-stage or later base — following a breakout from a cup with handle, saucer with handle or double bottom — during a stock’s major uptrend.