This code should work:
a = torch.arange(0, 3).unsqueeze(0).unsqueeze(2).expand(2, -1, 4)
b = torch.arange(3, 6).unsqueeze(0).unsqueeze(2).expand(2, -1, 4)

c = torch.stack((a, b), dim=2)
print(c.view(2, 6, 4))

Note that I initialized each  channel with a certain value, so that you can check the interleaved result.