This is an 8 x 8 piece of masonite (hardboard) from the local Lowe's store. My husband cut it to size from a large sheet. Onto this, I have applied a coating of Sennelier acrylic red gesso (link). A rough placement sketch is made using a blue Stabilo CarbOthello pastel pencil (link). These pencils are easily erased with a finger. I think it important to note that the placement sketch is a rough guide for the large painting elements. If I make a beautiful drawing, I am tempted to complete a paint-by-number "in the lines" piece that is inevitably too tight.
I like to have areas where the red shows through. Sometimes the red is left as unpainted areas. Othertimes, it seems to add a red essence.
The red ground also forces me to apply a decent thickness of paint (I continue to struggle with wanting to "save paint" and smear too little paint into many areas).