I promised to post some pictures of how the ice cube tray onigiri came out so here they are with step by step photos! My flash was abit of an overkill but i hope the photos look okay.
First I sprayed my tray with some oil
all nice and oiled
(if you look closely you can see my penguin tray in the background)
Fill the tray up with short grain rice from my rice cooker
pop in the freezer for just a minute to let them cool down
and voila! blossom/rounded star shaped onigiri!
the flash killed this picture, my apologies
and the onigiri in action along with my first bento!