The Osmo Large Carrying Case is specifically designed to fit the new Osmo Base for iPad, the Osmo Creative Board, and up to four Osmo games (depending on stackable storage container size). The overall dimensions are: 12.6 inches long x 11 inches tall x 3.5 inches deep.
For reference, the neoprene pouch in the Osmo Large Carrying Case can also fit a compatible iPad. However, the case cannot fit both an iPad and the Creative Board at the same time without damaging the case and Creative Board.
You can find more information about the Osmo Large Carrying Case here:
Here is a picture of the Osmo Large Carrying Case for reference: