Moss control

I am building a small 4' x 4' sandpit. That area of land currently has moss all over it. I have removed the top layer of mud/soil with a spade and taken all the moss out. My plan is to use 2x6 lumber to build the sides of the sandpit, lay landscape fabric down in the enclosed 4'x4' space and then put in playsand.
Do I need to do something else to the soil before laying the landscape fabric down, to prevent moss or other wetness related problems that may arise with the sandpit?
Thanks Bob
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