Phonics

Adding a vowel suffix (ed, ing, est,er, ous) to a one syllable word (1),  with one vowel (1) followed by one consonant (1) NOT in the Black Box W,X &Y, double the consonant ending of the base word and add the vowel suffix.

lap + ed = lapped (adding vowel suffix to a 1 syllable word which has 1 vowel followed by 1 consonant (and it’s not w, x or y) so we double the p and add ed)