C# create instance of abstract using reflection

I met a task in which it is necessary to create an instance of an abstract class using reflection on C#. At the same time, it is forbidden to create heirs.

It is clear that it is forbidden to create such instances, but reflection helps to overcome this. The answers were advised to look in the source codes on the referencesource site, to look for something like an internal call to the constructor through reflection. A hint in the task: need to find a method in the framework that directly deals with calling the constructor and simulate its logic without unnecessary checks. But I can't find. I find how to create instance of abstract class, but without initializing variables.

How can create such an instance so that class variables with values, if they exist are also initialized?