Originally Posted by
Tu.114
A sloping runway, be it up or down, will influence that sink rate. An upsloping runway will come up to meet You, a downsloping one will shy away from You. In the first case, Your effective sink rate is higher, in the second case, lower. So with an upsloping runway, flare a tad earlier and more; with a downsloping one, later and a little less. If done right, You will achieve roughly the same body angle on touchdown relative to the runway, whatever the slope may be.
Nice and easy explanation!
I would like to add the effect of increased (or reduced if the opposite) vertical speed: high temperature on RNAV approaches (high temp, steeper approach), high elevation airports (more altitude, for the same 3º glidleslope, more groundspeed and more vertical speed as well) or some tailwind of heavy weight; in those cases runway will be coming faster to meet you.
Think about those things and plan to make minor adjustments on your flaring technique. After a few hundred landings you'll get it.