Many modern easels attach to camera tripods using a quick release plate. You can make a much secure mount if you buy an additional plate and screw it semipermanently into the base of your easel.

Sample from the instructional video "How to Make a Sketch Easel"
Download available at Gumroad: https://gumroad.com/l/sketcheasel

Also, check out "Gouache in the Wild": https://gumroad.com/l/gouache
and "Casein Painting in the Wild": https://gumroad.com/l/casein

Gurney's videos also available as DVDs: http://kunaki.com/mSales.asp?Publishe...