Use 2 strands of 4-ply together,
J Hook (Gauge 5 DC = 2"; 2 rows = 1 ½ ")
[NOTE: I crochet loosely - be sure to check gauge] If you crochet tightly use a larger hook

Small [Womans 7-8, Mans 6-7]
Medium [Womans 9-10, Mans 8-11]
Large [Mans 12-14]

Round 1: Using two strands held together, Chain 4. In 3rd st from hook, 9 DC. Sl st to top of Ch 4. Ch 3 [NOTE: for a "wider slipper" do 11 DC]

Round 2: 2 DC in each st; sl st to top of ch 3. Ch 3

Round 3: 1 DC in each st; sl st to top of ch 3; Ch 3

Rounds 4-5-6: repeat Round 3 [For Size Med.+ Large Repeat Round 3 for Round 7]

At this point, work is done in rows instead of rounds.
Row 1 - DC in each stitch to last 5 stitches for top of slipper; Ch 3, turn

Row 2-3-4-: DC in each st, Ch 3, turn [For Large, repeat for Row 5]

Row 5 [6 for large] DC in 1st 6 st; Dec 2x, DC in remaining st. (forms heel)

Holding WRONG sides together, sl st from top of back of slipper to bottom of heel; fasten off; tuck in end.

Top of slipper:
Row 1 ATTACH yarn to top of heel; Ch 3. Work 2 DC in each st around side [If 5 rows, there will be 10 DC]. At top of front slipper – DC 1x, 1 DC, DC 1x, Work 2 DC in each st around side. Sl st to top of ch 3.

Row 2 - 1 DC in each st; sl st to top of ch 3.

Row 3; Repeat row 2

Row 4: Alternate front post/back post stitches to form light ribbing. Sl st to top of ch 3; fasten off, tuck in ends.