If the 737, fly the whole procedure with both FD and autothrottle switched off. Abeam the landing end of the runway lower the gear and appropriate flap and the speed will slowly reduce to the desired for the flap setting by the time you are ready to turn base 45 seconds later. Use the standby ILS to pick up the first indication of glide slope position on base and adjust your profile to pick up that glide slope nice and early before the PFD ILS appears in view.
A handy rule to remember on how long to go downwind after passing the end of the runway is 15 seconds if carrying out a 500 ft low level circuit. 30 seconds for a 1000 ft circuit and 45 seconds for 1500 ft. This works for the 727 as well as the 737.
If flying the Classic 737 at flap 5 and 180 knots downwind, you will find that if using 30 seconds timing and then lowering the landing gear and selecting flap 15 while at the same time turning base as the 30 seconds comes up, the whole game gets too rushed and it is too easy to get quickly high on glide slope if your circuit width is correct at 1.5 miles.
It is less feverish if you drop the gear abeam the end of the runway and using 45 seconds before turning base. The Boeing FCTM lacks advice on timing and it is left to airmanship.