Let's try this with a slightly smaller matrix, so you can see what's going on.
Let's slice this into 3-by-2 chunks. We don't actually need to slice it row-wise (since we want each chunk to have 3 rows just like A has three rows) but we do need to slice it column-wise.
columnSliceSizes = [2 2 2 2];
C = mat2cell(A, rowSliceSizes, columnSliceSizes)
Now let's slice A into a 2-by-3 cell array. Each cell in the first row of the result should contain 2 rows of A and each cell in the second row should contain the third row of A. Each cell in a column of the result contains 3, 2, and 3 columns of A respectively:
D = mat2cell(A, [2 1], [3 2 3])