One way (slicer machine start print gcode), or another (PRINT_START macro), there's certain steps we need to take to start printing the gcode that's slice from an object. There's reasons and rationale for why you'd place certain actions where.

• heat bed
• home and position
• heat extruder
• prime nozzle
• reset extruder

• heat bed
• home and position
• heat extruder
• Set the feed speed to 100%
• Set the flow rate to 100%
• prime nozzle
• reset extruder

;
; Orca Slicer Machine Start G-code by @dshoop v2.1
;

; PRINT_START 
; note the above line is commented out as we may or may not need to call this depending
; on our version of Klipper. If earlier versions of Elegoo's distribution it 
; was called automatically. 

G28; Home, if this fails no point to continue
M190 S[bed_temperature_initial_layer_single] ;wait for bed to reach temperature
M104 S150 ;pre-warm extruder to 150C below typical extrusion temps so as not to ooze, no wait
;
BED_MESH_CALIBRATE mesh_min={adaptive_bed_mesh_min[0]},{adaptive_bed_mesh_min[1]} mesh_max={adaptive_bed_mesh_max[0]},{adaptive_bed_mesh_max[1]} ALGORITHM=[bed_mesh_algo] PROBE_COUNT={bed_mesh_probe_count[0]},{bed_mesh_probe_count[1]} ADAPTIVE=1 ADAPTIVE_MARGIN=0
;
M104 S[nozzle_temperature_initial_layer] ;Heat extruder to temp, no wait
M220 S100 ;Set the feed speed to 100%
M221 S100 ;Set the flow rate to 100%
G90
G28 ;home
G1 Z10 F300
G1 X67.5 Y0 F6000
G1 Z0 F300
M109 S[nozzle_temperature_initial_layer] ; wait for extruder to reach temp
G92 E0 ;Reset Extruder
G1 X67.5 Y0 Z0.4 F300 ;Move to start position
G1 X167.5 E30 F400 ;Draw the first line
G0 Y0.6 F120
G1 X67.5 E60 F400 ;Draw the second line
G0 Z0.6 F120
G92 E0 ;Reset Extruder

[gcode_macro PRINT_START]         
gcode:
	RESPOND PREFIX="" MSG=">> PRINT START <<"
	M117 Starting Klipper START_PRINT code
	M400	; wait for current moves to finish
	CLEAR_PAUSE
  	M105 ;Request a temperature report to be sent to the host as soon as possible
	RESPOND PREFIX="" MSG=">> GCODE START <<"
  	M117 Executing gcode