A power miter saw can provide very accurate straight cuts and a table saw with support extensions can make all types of cutting easier. Size of your deck which can be determined in either. Set a circular saw to a 2-inch depth of cut and cut the outside edge along the cut line.
Im building a DIY floating deck in my back yard.
The angle of your decking. This is an old furniture makers trick. Store your deck boards before installing. Frame WaterproofingPart 3.