Stand in front of the chair with your feet under it and the knees touching the seat. (fitnessandpower.com)
Practice by actually standing in front of a chair and sitting down on it briefly before standing back up. (verywellfit.com)
Sit on the floor in front of a chair with your legs crossed, with enough blankets on the seat so your forehead can rest on the blankets without strain, or if this is difficult, sit with the legs straight under the chair. (yogajournal.com)