Although there are three letters in the word 'six', there are four separate phonemes. This is because the letter 'x' has two phonemes - k and s.The phonemes, or actual speech sounds, in six are s / i / k / s
The silent letters in the word "know" are the 'k' and 'w'. They are not pronounced when saying the word.
There is no English word that uses all those letters, but here are some six-letter words: swarth, thraws, wraths.
No eight letter words match that description. However, a seven letter word, basking, and a six letter word, asking, contain a portion of those letters.
bakerybikingbakinghikingjokinglikingmakingpokingrakingtakingwaking
skunks
creams
Some six letter words with second letter U and fourth letter K are:bucketbucklebunkercuckooduckedduckiehunkerhuskedjunkedjunkerjunketluckedlurkedmuckedmusketmuskoxpuckerpunkedquakesruckussuckersulkedsunkentuckedturkey
skinny
j-o-k-i-n-g?
I could only find one word ending in "kr" and it doesn't start with an "f" or have five letters. Perhaps you're thinking of a six-letter word.askr
squawkstreak