Web alarm clock for 11:03 a.m.
You are preparing the rice seedlings, tying the bundles and checking the route to the flooded paddy before they need to be moved. Set the alarm for 11:03 am so the remaining preparations have a clear stopping point. With 12:00 pm approaching, you can keep the seedlings shaded, ready the trays, and avoid leaving the transfer until the midday heat.
Because the rice seedlings will need prompt handling, test the alarm sound now rather than discovering later that it is too quiet. Set a near-term trial, raise the volume to a level you can hear from your work area, and confirm that the tone plays clearly. Then return the alarm to 11:03 am. Keep this page open and the phone awake: if either is unavailable, the rice seedlings may remain waiting because the browser alarm will not sound.
While you arrange the rice seedlings in late morning, listen to how the surroundings change near 11:03 am. Voices, tricycles, farm equipment, and movement around the paddy may grow louder as noon nears. Place the phone close enough that the signal stands out without being buried under that activity, but keep it on a dry, stable surface away from splashes.