VOICED POST-DENTAL STOP [d]
VOICED POST-DENTAL FRICATIVE [ð]
Dal with dagesh is pronounced similarly to English "d", except the tip of the tongue is placed behind the teeth on the gums instead of on the teeth themselves. Dal with rafe, which typically occurs after vowels, is pronounced with the tip of the tongue in the same place (i.e., on the gums behind the teeth), but with an allowance of air to pass through to make a fricative sound. For those familiar with Arabic, it is pronounced like the letter ḏāl (ذ).
EMPHATIC VOICED POST-DENTAL FRICATIVE [ðˁ]
In the environment of other emphatic sounds—at least in two such words—אַפַּדְנ֔וֹ 'his palace' (Dan. 11.45) and וַֽיַּדְרְכ֤וּ 'and they bent' (Jer. 9.2)—the post-vocalic fricative דֿ [ð] tended to undergo pharyngealization/emphaticization and came to be pronounced as an emphatic like Arabic ظ ḏ̣āˀ. Pronounce this sound just like dal rafe but with the "root" of the tongue retracted and greater pressure/tension exerted in the pronunciation.
SOURCES AND FURTHER READING
Khan, Geoffrey. 2020. The Tiberian Pronunciation Tradition of Biblical Hebrew. Cambridge: Cambridge and Open Book Publishers. §I.1.4.