Dividing the matrices into submarines

N is the size of the matrix, K is the size of the submarine.
The matrix is further introduced
Accept N = 3, K = 2Our N*N matrix.
1 2 1 1 1 2 1 1 1
All size submarines K*K:
[1 2 1 1]
[2 1
1 2][1 1
1 1][1 2
1 1]
How do you do the same job finding a submarine? What do you want me to do?
The only thing you've done is create a threedimensional set of k*k matrices filled with zeros.

If in the forehead,
matrix = [[1, 2, 3, 'a'], [4, 5, 6, 'b'], [7, 8, 9, 'c'], [10, 11, 12, 'd']] size = (3, 2)
for j in range(len(matrix)  size[1] + 1):
for i in range(len(matrix[j])  size[0] + 1):
for y in range(size[1]):
line = []
for x in range(size[0]):
line.append(matrix[j + y][i + x])
print(line)
print()
In a blatant way, you have to go through the matrix so that one element of the submarine is within the range:
matrix_width  submatrix_width
♪matrix_height  submatrix_height
And then using the coordinates of the first element, find all the other submarine elements in the matrix.
or if it is written at the formula level, then:
submatrix[x][y] = matrix[i + x][j + y]
where (i, j) is the coordinates of the first (left top) submarine element in the matrix
P. S.
The code can be slightly simplified (for disgusts):
[[[print([matrix[j + y][i + x] for x in range(size[0])]) for y in range(size[1])] + [print()] for i in range(len(matrix[j])  size[0] + 1)] for j in range(len(matrix)  size[1] + 1)]