It's a work in progress, but here's my pochade box project:
Picked up a beautiful cigar box in a local smoke shop in Escondido, CA
I did a fair bit of research and decided, since my media would be watercolor, I didn't need a tilty lid.
I removed the hinges and installed neodymium magnets to hold the lid. Between the back and front magnets. I reversed the polarities so flipping the lid to the flat inner side, practical for sketch and paint, wouldn't be a hastle.
Due to the magnet's strength, there is absolutely no worries of the lid coming off, the latch furthermore insuring there to be less slidingaction.
Lid held up via being propped on the box and leaning on chair backrest.
I went on to pick up some bass wood from an arts and crafts store, and cut it into compartment spacers. There is also an extra piece to divide the box hieght-wise, dividing unused paper from space for drying or held pieces of work, from supplies.
Further goals for this project are to devise magnetic detachable side planes to hold altoid tins for palette mix, and the collapsible water cup; as well as devise a handle for carrying the box.