Official description from National Emblem and National Flag of the Republic of China Act (中華民國國徽國旗法):

Symbols

天, 地, 人, 和 = red field
天, 日, 月, 星 = blue rectangle
甲, 乙, 丙, 丁 = white sun
Ring between 甲, 乙, 丙, 丁 and 戊, 己, 庚, 辛 = blue ring
子, 丑, 寅, 卯, 辰, 巳, 午, 未, 申, 酉, 戌, 亥 = top angles of the 12 white rays
中 = center of the white sun
中, 甲 = radius of the white sun

Sizes/Radius

(Subparagraph 1, Article 4) 天地 : 天和 = 3:2
(Subparagraph 2, Article 4) 天日 = 天地/2
⁠天星 = 天和/2
(Subparagraph 4, Article 4) 中甲 : 天日 = 1:8
(Subparagraph 5, Article 4) Applying following subparagraphs
(Subparagraph 3, Article 3) 中子 : 中甲 = 2:1
(Subparagraph 4, Article 3) 甲戊 = 甲丙/15
(Subparagraph 5, Article 3) Each angle of 子, 丑, 寅, 卯, 辰, 巳, 午, 未, 申, 酉, 戌, 亥 points = 30°, totaling 360°
(Subparagraph 6, Article 3) angle 子 faces north
⁠angle 午 faces south
⁠angle 卯 faces east
⁠angle 酉 faces west

Description of Geometric Drawing

1. Draw a horizontal line from 和 point with 天 point, and a vertical line with 人 point. Make lengths between 和–人 line and 和–天 line being aspect ratio of 3:2. From 人 point to draw a 人–地 line parallel to the 和–天 line. From 天 point to draw a 天–地 line parallel to 和–人 line, forming the 天–地–人–和 red field.
2. Equally divide 和–天 line equally in 星 point, and divide 天–地 line equally in 日 point, forming the 天–日–月–星 blue rectangle.
3. Equally divide 天–星 line horizontally and 天–日 line vertically, forming the crossing point 中. On the 天–日 line, take a 中–甲 line, make its length equivalent to 1/8 of 天–日 line. Use the 中 point as the center of the circle and 中, 甲 as the radius to draw 甲, 乙, 丙, 丁 circle, forming the white sun.
4. For geometric drawing of the blue circle and the 12 rays, see the description of geometric drawing for the national emblem for details.