Help Help uneven concrete area and Laminate flooring

[coloured]

Recently remove a carpet and putting down 12mm laminate flooring with a 5mm sonic gold underlay.
the room is 6m x 4m. the effected area is area is around after 4.5m as you see whether I have inserted a 5mm plywood and the red arrow
Would i be ok to just screw the ply wood to the floor and lay the flooring. worried about the edges of the plywood effecting the joints of the laminate.

 

[coloured]

is a 3mm gap acceptable like as in the picture

 

[Charlie George]

Use self levelling compound, if you lay the floor over that it's bound to bounce, for the sake of 15 quid or so it's a no brainer.

 

[coloured]

I did and follow the instructions of adding 3.5ltr of water to a bag and it was too thick to do much and set so quickly didn't have a chance to smooth over

 

[dazlight]

You be better with a decent bag & bottle compound like Ardex CL or Mapei latexplan