Safespot east of Castle Wars (west of Yanille). Stand between the plants and the dry stone walls. In this spot, you have a wide field of view and the ogres can never reach you.
The best place to kill ogres for Slayer is directly west of Yanille, near where Og is situated and the small island, although the location may be crowded with cannon users that can make training there inhospitable; if that's the case, it is possible to kill the ogres camping in the ruins immediately to the north, behind a line of trees, as those are not affected by the cannon.
Alternatively, if the player has level 46 Thieving, they can access the Chaos Druid Tower that has 7 ogres in its dungeon, where it is usually quiet. After completion of Biohazard, caged ogres found in the Combat Training Camp can also be fought using ranged and magic; melee in the training camp is possible if using a halberd to attack the ogres through the caging. These ogres are unaggressive.