There is only the observable Universe.

The Universe is expanding at exactly the velocity of light.

This explains cosmic isotropic as 'c' has always been the same.

The Universe is closed, positively curved and asymptotically flat.

Derivation of the Hubble-Slipher Constant for a Universe age

of
13.8 billion years given a velocity-of-light
expansion rate.

Kilometers in a megaparsec: 3.08567758 × 10
^{19}

One year = 31,556,926 seconds

Universe at age UAge is t = 13.8 billion years.
Assumed.

Universe UAge is t = 31,556,926 × 13.8 × 10^{9} = 4.354855788 × 10^{17} seconds

Diameter ct = 299792.458 km/sec × 4.3548557 × 10^{17} sec = 1.3055 × 10^{23} km

Diameter is ct = 1.305553 × 10^{23} / 3.08567758 × 10^{19} mega parsecs

Universe Diameter is ct = 4231.009 mega parsecs

Hubble-Slipher Constant is H = c per UD = velocity of light per Universe Diameter

H_{0} = 299792.458 km/sec per 4231.009 mega parsec

H_{0} = 70.856 km/s per Mega Parsec

Derivation of the Hubble-Slipher Constant for a Universe age

of
14.5 billion years given a velocity-of-light
expansion rate.

Kilometers in a megaparsec: 3.08567758 × 10^{19}

One year = 31,556,926 seconds

Universe at age UAge is t = 14.5 billion years.
Assumed.

Universe UAge is t = 31,556,926 × 14.5 × 10^{9} = 4.57575427 × 10^{17} seconds

Diameter ct = 299792.458 km/sec × 4.57575427 × 10^{17} sec = 1.37177662; 10^{23} km

Diameter is ct = 1.37177662 × 10^{23} / 3.08567758 × 10^{19} mega parsecs

Universe Diameter is ct = 4445.625 mega parsecs

Hubble-Slipher Constant is H = c per UD = velocity of light per Universe Diameter

H_{0} = 299792.458 km/sec per 4445.625 mega parsec

H_{0} = 67.435 km/s per Mega Parsec

For different assumed Universe Ages here are corresponding Hubble Constant values.