These take guesswork out
https://www.amazon.com/dp/B073VS72R3/ref=cm_sw_r_sms_api_glt_fabc_97MPMDXQ51XEFCYBWDNW
I'm pretty sure you wanted to respond to the OP. I've been using dowels for over a decade as my exclusive joinery method. I recommend Jessem dowelling jigs.
As for the "flag" on the drill, drill stops are more effective and reliable.