How do I stretch my feet so that i have a better arch?

I am gong on point (well, pre-point this summer and point in the fal. Pre-point is where you practice intensly on going on point so you will be strong enough for point cles. we are using point shoes and will be going on point ALOT!)) and i was told that my arch on my foot when i point is very good but it needs to be just a little longer. They recommended that i stretch my foot. How do I do that without damaging my feet. I need to be able to do these in 4-6 weeks. I am very flexible (so dont worry about that) Plz help.