My main easel for RC paper, is a rectangular piece of chipboard which measures just over 300x400mm or 12x16".
Attached to two sides, are some flat strips of timber sticking up about 6mm. I just push the paper into the corner and fire away.
I have outlined all the paper sizes I use with a ball point pen, not for positioning the paper, just to give me an idea for rough framing after first inserting a negative.
Been using it for 20 odd years and have always meant to make a better one using MDF with a smooth finish, one day I will.
I also have a Jobo 8x10" Varioformat which is excellent, but for whacking RC prints through, nothing beats this except a roll easel.
Mick.