How to create a 2D array from the first column of a 3D array?

I have a 3D array of size(N,N,sz). I want to create a 2D array of size(N,sz) where the columns of the 2D array correspond to the first column from every sz-th array from the 3D array. I have tried the following but there is a "Subscripted assignment dimension mismatch" as an error:

   2Darray=permute(3Darray,[1 3 2]);
   2Darray=reshape(2Darray, [], size(3Darray,2),1);

   for m=1:1:sz
       2Darray(:,m)=3Darray(:,1,m)
   end

Answer 1

[Guillaume]

2Darray = squeeze(3DArray(:, 1, :));
%or
2Darray = permute(3DArray(:, 1, :), [1 3 2]);