I looked into this recently and started a thread about it.
I’ve got a standard 142mm rear hub to work in my 148mm new frame. I had to buy 2mm and 1mm M12 washers, 1 of each either side to space out the hub to the frame. I then bought a load of M5 1mm washers to space out the rotor from the hub 3mm, or you could get 1mm M6 washers and space in the caliper if you have an IS mount frame (3mm washers of any size are a bit difficult to come by). Remember to check your frame dropout clearance against the outside diameter of the washers too. I had to get 20mm OD M12 washers.
Oh if you go the rotor space out route don’t forget to get some longer rotor bolts. I got 15mm long ones for mine.
I’ve ridden it a couple of times and it all works. The caliper alignment is a bit fiddly and the shifting in a couple of gears I can’t get quite right. I’m a little worried about putting stress on the frame axle though as the hub axle obviously doesn’t sit in the dropouts, the washers do.
Ultimately I got it working but my OCD won’t let the little grumbles lie so I’m going to buy a boost wheelset and shift the current wheels onto my Aeris. Depends what you’re will to accept I guess.
HTH