Roughly sketch the composition, its a good idea to design your composition so that painting in the poppies will be easy, so draw the petals touching each other.

Wet the sky with clean water. Drop in raw sienna just above the horizon line and allow to dry. Wet the sky again with clean water drop in cobalt blue - if it runs into the flower shapes dap out with kitchen paper

Dry - Paint roughly wet-in-wet the foreground with blue+yellow and red around the petal shapes note the background is different colours in mid tones, add some darker greens for leaves.