Analyzing the wireless environment for signal strength and interference using a WiFi analyzer is the best initial approach for troubleshooting slow AP association times. A WiFi analyzer can help detect issues related to signal strength, interference from other wireless networks, or environmental factors which could contribute to slow association times, without the need to make immediate configuration changes or disrupt current users. Changing AP locations or antennas could impact the current setup and user connections significantly. Disabling security features is not advisable as it compromises the network's security. Updating the firmware without preliminary analysis might not address the root cause and can be disruptive if not done carefully. Changing to a less congested wireless channel may improve performance; however, it's a less specific course of action compared to using a WiFi analyzer to diagnose the issue thoroughly before making changes.