4 x 2 joists screw fixing

I am putting a few 4 x 2 timbers at right angles on top of the existing 4 x 2 joists in the loft to raise the height for loft insulation and board on top for storage.

What is the best way to screw the timbers down to the joists.

Straight through the top of 1 joist vertically down in the joist below, guess I will need somthing like 150mm screws ?

Or from ½ way down the height of the side of the top timber angled down into the one below. Think it is called Skewing?

What length screws would be best to use?

thanks for your help

4.5 or 5x80mm no8 or no 10s 3" enter 2" down at around 30deg
dont worry because the screw will pull down around 20mm giving you 45mm in the bottom

Thanks, that’s the loft insulation all topped up and 2m sq boarded area to store the Xmas decorations etc!