Newbie help please

[Rburnham82]

Hi guys

I'm new to the forum and 3d printing in general. I have a anycubic mega s printer using cura software. I am having trouble printing a certain thing and feel there must be a easier way. So I am printing a frog shape flat piece, then a square with the same frog shape cutout, so the frog shape fits inside the cutout. Trouble is when I print them because they are the same size obviously they don't fit. So if I make the frog shape 1 percent smaller than the cutout shape it still doesn't fit as it's it still doesn't line up.
Am I missing something really simple or can someone help me please.
Hopefully that makes a little sense.

Cheers
Rich