Try These Core exercises for your obliques instead of russian twists
Side Plank Variations
Side plank same knee/elbow crunch.
Side plank with hip abductions.
Form - draw your belly button in towards your spine and push your body away from the ground, especially in the shoulder; Maintain head, shoulders, hips and feet in alignment.
Side V Up
Legs straight, Arm straight .
Longer lever therefore harder.
Modification: side crunch with knees bent.
Draw belly button in towards your spine throughout exercise.