On-PCB SPI Distance Considerations
At 1MHz you have nothing to worry about. I've committed atrocities such as passing 8MHz SPI over 30cm ribbon cables with impunity (maybe I got lucky!)

When you go higher, say, 30MHz, you have to start worrying about controlled-impedance traces, matching lengths, not taking sharp turns or having vias, and so on, but you are nowhere near that operating regime.