Most of the time your iPhone can get a good GPS signal in <10 seconds. But if you're having issues, you can try the following:
- Make sure you're outside; being indoors can degrade the accuracy of your phone's GPS.
- Let Slopes get a good GPS fix before you turn off cell data or wifi as those can speed up the acquisition process.
- Make sure Airplane and Low Power modes are off as they do affect the accuracy of your GPS. Turn off cell data instead.
- Try keeping your phone in a different location. Some clothing materials really hurt GPS reception, or you might have it under too many layers.
- Head to the settings for Slopes (under About tab), go into Location Services, and toggle access off and then back on.
- Worst case, reboot your phone. This is rare, but I've seen it fix poor GPS reception issues.