The layout consists of adapting your board lengths according to your terrace. To define the number of rows, simply divide the width of your deck by the width of your wooden boards.
You know which way to lay your boards, the number of rows of your terrace. Now, for the realization of your wooden terrace on pedestals, think about the layout of your pedestals. Their spacing will depend on the type of wood chosen.
For a softwood deck like pine, plan to place joists every 50 cm.
For an exotic wood deck, whatever the species, favor the placement of joists every 40 cm.
For both, consider placing pedestals at equal distances every 70 cm.
Clearly, the spacing between each of your joists will be 50 cm (or 40 cm) and each of them will be supported by studs placed every 70 cm.
The pedestals will not be the only elements to be provided: joists, geotextile felt, bituminous protective strip, board spacers and special wood screws are also to be calculated on your layout plan.
Note, for optimal stability and a beautiful finish, favor a staggered cut rather than an alignment of the boards. For example, for a 10 m long terrace, it is better to make three cuts (two of 4 m and one of 2 m) rather than two of 5 m.