Select Edge - Ring

1. Select Edge - Ring it

2. Select poloygon face mode

3. Select "connect" to add an extra edge

4. Extrude inward or outward depending on where you want it to be

Editable Spline - value of 1

thickness

fills the void

welding

Displace Modifer - surface - displace map

increase strength

cellular - wide spots are getting bigger