I like 2mm Seyes paper, because it's a convenient sort of x-height, and also because the quality of Clairefontaine at least is excellent. I don't tend to use slant guides now, but used to slip a sheet underneath. It's good for practice, having closely spaced lines to give the heights for ascenders and descenders too.
You'll note that the vertical ruling divides the page into squares. If you count off four squares down and three across and join the opposite corners of the rectangle, that will give you approximately 53°, which is quite handy. If you're a stickler for accuracy, 9:7 will give you the merest shade over 52°. So it's not too difficult to construct the slant lines if required without recourse to tiresome things like protractors or adjustable set squares. A rolling ruler would be jolly handy, though.