Identify the 19mm pine floorboards by their length. Start with the first floor board parallel to the wall of the cabin. Ensure that the tongue of the board is facing away from the wall. Allow a small gap to allow for the natural movement of the wood.
The chamfered corners should face downwards to provide a flatter top surface. Fix the first board with nails in each of the pressure treated bearers. Now take the remaining floor boards and fix them one after the other, making sure that the tongue and grooves fit together perfectly. You may need to saw the boards in places to fit around any strengthening walls. If the last board is too wide to fit, measure the remaining space and saw the board to fit correctly, it is best to not fix the last few boards until the last one has been sized and fitted in place flat down.
If the floor is long, the floor boards will be in two or more lengths. It is best to stagger the joint, so on the first line lay a short board then a long board and on the next line lay a long board then a short board. Continue the alternating sequence as you cover across the floor.
On the parts list find the floor finishing slats. These fit neatly around the walls, on the floor to hide any gaps between the floor boards and the walls.
Once the floor has been laid it is a good tip to cover it to keep it clean while you continue the construction.