I use photo corners that you can get at any craft store.
https://www.michaels.com/recollections-clear-photo-corners-250-ct/10202263.html?cm_mmc=PLASearch--google--MICH_Shopping_US_N_Papercraft_N_N_N_N--Papercraft&&cm_mmc=PLASearch--google--MICH_Shopping_US_N_Papercraft_N_N_N_N--Papercraft&gclid=CjwKCAjwiZnnBRBQEiwAcWKfYtoyFDhFh3p1RP6rcgTImGHs4GGmNQMqvLJNObnhlkcvHcyrLLrneRoC3ZIQAvD_BwE&gclsrc=aw.ds
They do not ruin the photo as no adhesive on the photos. Lay the boards flat, layout the photos and then add the corners. I have my sons and nephews do this for my father-in-law’s memorial sitting in the hotel courtyard as i couldn’t fly with the photo boards.