I really WOULD NOT reccomend putting the soil into your tray, rather get a plastic pot bigger then the one you have now and fill it 2/3's or 1/2 full (better to put more as to not have this problem again) with soil and place your plant (with the pot it's in, obviously) into that, allowing the exposed roots to take cover...

Also, you should no that the roots of the kind tends to grow more horizantally, when it reaches a barricade (the side of the pot) it tends to grow straight down, unless you practice good watering habits, which I can't tutor on since I'm not that good at that.