Best method to drive SPI over 1 m
1m is not that much. Even in noisy environment good shielding and low speed should be enough to achieve reliable communication. That is, unless you are going to run this thing next to aircraft radar or ark welder.

A simple solution would be to use shielded CAT5/6 cable. One twisted pair would be SCK+GND, another MOSI+GND, and the remaining 4 can be used for 3-bit slave address and enable line. You'd need a shielded jack on master side, of course.

On the slave PCB a 3-to-8 decoder, like 74HC138D will convert 4 control lines into low level on one (or none) of the 8 output pins, suitable for direct connection to !CS inputs.

And if you ever decide to increase speed or noise immunity, you can always convert those two signal+gnd pairs into differential lines, as @User323693 suggested. There are convenient dual driver/receiver chips like SN65LVDS9638 and SN65LVDT9637B for this. There is no need to modify address control lines in this case, although you'd have to connect shield to the ground on slave board too.