I share the opinion of @chefpeon
Although I somewhat disagree about the cornstarch not being acid stable but I agree that cooked-up (native) cornstarch is not very freeze/thaw stable (as it's called in industrial food science) particularly if it's not cooked up first. Commercial bakeries use modified cornstarch to obtain good freeze/thaw stable gels. You may investigate this ingredient from your ingredient supplier.
Otherwise, if you wish to pursue with ordinary cornstarch, my suggestion is to fully cook the filling separately (on the stove top) and add the once cooled filling to a very cold uncooked formed pie crust then immediately proceed to freezing the product. This way the filling will not leach into the uncooked dough while it's thawed/liquid and before it cooks (gels) up. Also quick freezing will also minimize leaching.
Also, by doing it this way, the filling will not bubble-up excessively (because it will by already thick) and spill over the pie crust.
@Luc_H, I'm not even sure you know what you're talking about because you completely contradicted yourself. First, you wrote:
I agree that cooked-up (native) cornstarch is not very freeze/thaw stable (as it's called in industrial food science) particularly if it's not cooked up first.
First of all, this sentence left me scratching my head. Huh? Second, you agreed that cooked up native cornstarch is not very freeze/thaw stable, which is absolutely true.
I know from personal experience in production pie making, and regarding other cornstarch thickened items, such as pastry cream for example, that if you "cook it up", then freeze it, you're gonna have a bad time. I froze pastry cream once. I can tell you, it breaks down and turns into an unsalvageable soupy mess. Anything else you cook up with cornstarch yields the same result. It breaks down if you freeze it.
Then you write:
Otherwise, if you wish to pursue with ordinary cornstarch, my suggestion is to fully cook the filling separately (on the stove top) and add the once cooled filling to a very cold uncooked formed pie crust then immediately proceed to freezing the product.
See what you did there? You just told the OP to do something we both agree does not work.
If you are going to make up pies to freeze and bake off later, and your filling is cornstarch thickened, you DO NOT pre cook the filling. You toss the fruit, sugars and spices/flavorings together, pour in pie shell, add top crust and freeze. If you cook up the filling first, make up the pies, freeze, then bake, the cornstarch thickened liquid breaks down and becomes runny.
You are right in your suggestion that using modified food starch, such as Clear Jel, eliminates much of the headaches:
I love Clear Jel. Not INSTANT Clear Jel though. I hate that stuff.
Lastly, I don't know if you see the message at the top of this forum, but if you're not a professional pastry chef, you are free to read, but refrain from posting here. If you are a pro or a former pro, perhaps you should change your moniker to reflect that. However, judging from this and past posts of yours, it seems to me that you are quoting from food science books and lack any real-world experience in the pastry business. The information you just contributed is confusing and contradictory and not helpful to the OP.