To better understand your sanchin stance it is a good idea to test the stance occasionally through various drills and training methods. Practice is the best way to see what works best and to develop automatic movement. The methods mentioned below are only suggestions but have been found to be useful and enjoyable in a class setting.

Method One
Working with a partner hold a long stick, approximately 6 ft. ( bo) or 2x2 board between each person at belt level. Place the stick on the abdomen between each person. Using sanchin steps, partner one will advance forward while partner two offers light resistance as his partner steps and forces his partner back. Do about 7-10 steps if room allows then without changing position go the other way. Pressure should be keep on the stick between partners so the stick does not drop as each person moves. Partner 2 is not moving unless his partner forces him back. Focus the abdomen while advancing forward.
The advancing partner should not lean into his step or take walking strides. The proper set up is to tuck and load the hips and pull the rear leg through (no lifting it off the floor), gliding along smoothly but forcefully.
Depending on the room size, do as many repetitions as possible then reverse direction.

Method Two
This is another training aide for sanchin step development and leg strength.
One partner will remove their belt and place the center upon their abdomen. The partner will stand behind them holding the two tab ends. The partner in the back will offer light pulling resistance while the partner being held by the belt sanchin steps forward. The following suggestions will assist in improving the step and leg strength if practiced regularly.
Focus the abdomen while advancing forward. Keep the knees bent and your back straight. The advancing partner should not lean into his step or take walking strides. The proper set up is to tuck and load the hips and pull the rear leg through (no lifting it off the floor), gliding along smoothly but forcefully. Depending on the room size, do as many repetitions as possible then switch.