Floating solid oak help!!!!

Basically there's only two things you can do with a concrete sub floor, you can use sika bond and then lay your boards on this, I've used this before its a bit messy but very effective. You can also use an underlay adhesive rolls, where you just basically peel the film off as you lay your boards I've also used this product to which is very effective too. From experience I would use underlay adhesive rolls. Hope this helps thanks

Unfortunately we would advise uplifting the floor and starting again as laying solid wood flooring floating on underlay is a disaster waiting to happen all solid wood floors of 18mm thick or more should either be glued to the subfloor with suitable flooring adhesive, porta nails or tongue tight flooring screws, the adhesive underlay is 1 other option but having used this ourselves we would not recommend this as a good quality finish and is cutting corners. The problems you will have if you float the flooring will be big gaps appearing between joints, major movement of the flooring due to expansion of the floor which would probably result in the floor pinching against the walls and this would then cause your floor to lift.