i tried using the reference plane but it did not allow me to align the holes as per the image. can anyone tell me how to model the leaf spring screw slots according to the image.
I think you'll want to use an assembly feature for this.
See my attached image. In this case I drilled clearance holes for 1/4" bolts through the two components. I also turned on the option to propagate the feature to the parts. This way the holes show up at the part level and not just the assembly level.
One more thing... Your sketch for the clamp needs to be fixed. Four of the "lines" are drawn as arcs. These should be lines.