Just take a Drive Down The Fretboard!
Imagine the 3rd, 5th and 7th fret dot markers as the lights of a traffic light. Then imagine drawing a triangle from the dot on the 9th fret to the pair of dots on the 12th to make a yield sign. Now each fret is unique:
1st: beside the nut
2nd: just outside the top of the traffic light
3rd: the red light
4th in between the red and yellow lights
5th: the yellow light
6th: between the yellow and green lights
7th: the green light
8th: in between the traffic light and the yield sign
9th: the point of the yield sign
10th: the narrow end of the yield sign
11th: the wide end of the yield sign
12th: the bottom of the yield sign
13th and higher: the previous frets, but in reverse
Now look at the neck of your guitar, imagine the images, say a number and then find the fret without counting. You did it, didn’t you?
You did it, didn’t you?