E.g.,
x = your 304 * 448 * 37 * 12 array
y = reshape(x,304,448,37*12);
Another possibility if you want those last two dimensions arranged differently is to permute them first. E.g.,
x = your 304 * 448 * 37 * 12 array
z = permute(x,[1 2 4 3]);
y = reshape(z,304,448,37*12);