A little advise regards loft boarding pls

hi i would like to put flooring down in my loft so that i can use it for storage. but im not sure how to do it.
1 would i screw the boards straight into the joist or should i lay wood battens down and put my flooring on there.
2 which way would the battens go? along the current joist or across the joists
3which way will the boards go?
4 what size battens should i use?
5 should the flooring go right to the wall and the the other vertical wood peices shown in the picture on the left the middle and right hand side or should there be a gap

the joist going horizontal are 2 inches wide and 4 inches deep
the vertical peice in the middle is 4 inches wide and 2 inches deep and the 2 vertical at either sides (maybe hard to see in picture, left one is more visable) are 3 inches wide and 9 inches deep
any guidance is greatly appreciated as we are trying to decorate the entire house and its a nightmare without space thank you all for for your time and advise in advance

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straight onto existing trusses, use loft floor boards as they will be right size for the spans (each board should go between 3) use an alternative pattern like you would lay bricks 1/2 overlap for each row and cut the ends to suit.

notch out the trusses enough to get cables flat under your floor and cut slots in floor round the roof supports

thanks just that a friend mentioned i should put 2x3 peice of wood across the joist or trusees (are they the same thing?)what is the benefit of putting 2x3 across what i have in the picture any ideas