Decide which things on your platter will need bowls, then place the empty bowls on the board. This is what I call a "put and look", then we will basically fill the board around them.
Then place larger items that will pretty much stay where you put them without spreading out too much. Things like bunches of grapes, fresh strawberries, and medium-sized cookies - and move around the bowls if they need it.
Then I start filling up the bowls. I do that now rather than at the end because I like to keep variations in colour throughout the board, so I like to work with the colour of these elements where they are going to stay.
Start filling in the gaps with things of contrasting colours until it's full!