Simply place a strong magnet, or three, on top of each easel blade, like Saunders, to keep the paper flat.
Likewise, using a thin anti-Newton pane of glass and a flat mild steel base, or a double thick easel base made of cabinet grade plywood, joined flat with glue, use some carefully marked Forster bits to make a series of holes the same size as a round, rare earth magnet, and hot glueing these in place (clean with alcohol to remove skin oils,etc) and once finished, with all magnets level, square to the top plain, make a temple of metal, cardstock, wallboard, etc, that has each magnet hole located in place, when lined up with the glass, covering the double weight paper, so additional strong magnets can keep it all aligned and flat in a single plain.
If you can afford it, the magnets touching glass, should have a coat or two of clear rubberized "Flexi-seal" spray, both sides, so they do no scratch, marr the glass nore have a hard metal to to glass impact when gently placing them at their stations.
I have some small, black painted wood bars with small embedded rare earth magnets that I use to use on a steel metal easel, without blades, to hold FB papers flat and give the negative image a border.
They can also hold notes on a steel wipe away ink board, above my sink, which is handy at times.
A last, simple solution is getting some granet store (no Home Depot or Lowe's) 3 CM thick sink cutouts from past jobs and cut, edge and polish them to fit one inside each of the enlarging papers or their boxes, in their various sizes.
Up to 16"x 20", you should be able to manage them OK, depending on your physical conditioning and use them as weights to flatten your printing papers a few days before exposing them.
After the prints have dried completely in a few days, you can again use them to flatten them as well, but use thick glassing papers between each finished print, just in case the papers are no yet dry enough, to prevent lifting the emulsion.
Cheers,
Eli
