Whenever I speak "I slept for~ hours yesterday/today or anyway" I have difficulty in pronouncing 'slept'.
I know how to pronounce popcorn, parlor, parrot, copycat and a single 'slept'.
But when I tried to speak slept for, for example, my mouth seems like I'm pronouncing 'sleft for' if I look mirror. I don't obviously sound 'f' sound in real. But when I speak 'slept', I my upper front teeth bite my lip. But when I pronounce 'slept for' after closing my eyes, it sounds like 'slept for' if I speak slowly but not very slowly. I tried to clearly speak 'slept for' repeatedly like I speak "I sleep for ~ a day(this sentence is not difficult to pronounce.)'. But my pronunciation of 'slept for' becomes even worse by speaking 'sleft for' 'slet for'.
How can I clearly pronounce 'slept for'? Or is there any trick to avoid speaking 'slept for' as 'sleft for' sleft for'?
(Sorry if I'm making too much confusion. I'm not sure I'm conveying what I intended somehow.)