For years now we’ve sold an incredibly versatile, inexpensive and open ended insert called the Basics Tinker lid for the Flisat Trofast tray 
We’ve now added these simple but really useful coloured hollow add ons to sit over the holes and are held in place when your tinker bowls are placed in. 
Buy the coloured acrylic set, or buy the simple MDF set which are engraved with shape names, plain on the other side if you want to colour them in 
(Please note we’re going to be adjusting the lettering on the MDF ones so they show up better once the tinker lids are in so photos to follow) 
There is the option to buy the insert too if you don’t already have one
Please note the add ONS rings do not come with the tinker bowls. An insert comes with all 6