Reversals (writing letters and numbers backwards) can be remediated by orienting students to the top left hand corner of their paper, and having them always start letters at the TOP.
Using a smiley face sticker or stamp at the top left hand corner of the page or worksheet can help. You can print and laminate THIS smiley face sign, and post it on the top left hand corner of your whiteboard, door, etc., and reference them frequently as a visual cue for your students.
This 😀 stamp can be used on worksheets you give your students, to help orient them to the top left corner.
These 😀 stickers can be placed on the top left hand corner of your student's desk, to help orient them to where we (generally) start our letters.
Re-teach and practice correct LETTER FORMATION. Try a multi-sensory approach to build correct motor memory. This may include practicing letters in the air, on the carpet, in sand, in shaving cream, etc.
If you have a student that reverses letters and numbers:
Choose one reversal per assignment to work on. If the child reverses many numbers, work on them one at a time beginning with the lowest number.
When using the slate chalkboard, use the "starting comer (smiley face)" and the child will quickly learn to form the letter the right way.
You demonstrate and have the child imitate.
For example, teach capitals B,D,F,K,L,P and R start with a big vertical line at the starting corner, then curves and little lines are added.
Allow the student to keep a letter strip at his/her desk for quick reference.
Some students may benefit from a green ("go") hand on the upper left hand comer of the desk and a red ("stop") hand on the upper right comer. This will sometimes clarify directional confusion.
Using the ''Handwriting without Tears" technique of wooden pieces and slate, master each formation before moving on to another.