You can just make a pie top, cook the filling then pop the top on, paint some eggwash on the top of the pie dish, then put the pastry on the top and put it back in the oven. It's easier to get ready made pastry if you are challenged in this area. Just roll it out to make it thin and pop it on the top. Or, you could roll it out, chop it in half to make 2 triangles, put the cooked filling inside the centre and fold the edges to make a smaller triangle so you'd get a pasty type pie.
especially if you make the top out of puff pastry, but cut out the size to fit the top of your pie and then bake it on a trrey on it's own and only top the pie once it is done. Then you get no soggy pastry.
Buying puff pastry is not cheating, it is sensible
I like pies with mash toppings, preferably a mix of mashed potato and sweet potato or mashed potato and swede (especially nice for chicken pies).