Newbie. No. Follow the technique book which says lower the toe of the foot to the floor immediately so that the foot is flat to the floor.
If you want the whole story it is.
Take the weight onto the LF and proceed as follows. Swing the Right leg forward from the hips, first with the ball of the RF foot touching the floor, and then the heel skimming the floor with the toe slightly raised. As the RF passes the toe of the LF the Left heel will be released from the floor, so that at the full extent of the stride the ball of the LF and the heel of the RF will be touching the floor. Lower the Right toe immediately so that the foot is flat on the floor.
With the body still moving forward bring the LF forward with just a little pressure on the ball of the foot and swing it past the RF to repeat the whole movment.
The knees should be easily and naturally relaxed. The legs are only straight at the full extent of the stride. even then the knees are not rigid. Don't think that the lady who is going backwards is a mirror image of your steps because they are not.
Having absorbed this information you would be well adviced to go to the Learning Center and look up the computer images , which you can copy, of a Forward and Backward Walk.
A little bit of extra advice. Stand side on to a table. Very slowly with the hand resting on the table for a bit of support, go through all of the above in detail including the raising of the heel of the standing foot as the moving foot passes. This is probably the most important part, which when we walk normaly we do without thinking. But tell us we are now dancing and we alter what is a perfectly normal movement. The only difference when we dance is there has to be contact with the floor. Which when we walk normaly we don't do because we don't need to. This is probably worth knowing as is all of the above. Dancing is just an exagerated walk. Good Luck.