The below pattern will form the basis of this challenge.

 /
 /
 /
 / 
 / 
// /
/ //
 /
 /
 /
 /
 /

Given an input width and height, each >=1, output the above ASCII art pattern repeated that many times, joining (and overlapping) at the small diamonds.

For example, here is an input with width = 2 and height = 1:

 / /
 / /
 / /
 / / 
 / / 
// // /
/ // //
 / /
 / /
 / /
 / /
 / /

Here is an input width = 3 and height = 2:

 / / /
 / / /
 / / /
 / / / 
 / / / 
// // // /
/ // // //
 / / /
 / / /
 / / /
 / / /
 / / /
 / / /
 / / / 
 / / / 
// // // /
/ // // //
 / / /
 / / /
 / / /
 / / /
 / / /

Rules and I/O

• Input and output can be given by any convenient method.


• You can print it to STDOUT or return it as a function result.


• Either a full program or a function are acceptable.


• Any amount of extraneous whitespace is acceptable, so long as the characters line up appropriately.


• 
  Standard loopholes are forbidden.


• This is code-golf so all usual golfing rules apply, and the shortest code (in bytes) wins.

Canvas, 26 25 24 21 bytes

４／╬/╬⁰ｒ：⤢ｎ⁸｛╵×↔¹Ａ×├ｍ↶

Try it here!

Explanation:

4/ create a 4-long diagonal
 ╬ quad-palindromize it - big inner diamond
 /╬ quad-palindromize "/" - small diamond
 ⁰r center the two added vertically
 :⤢n overlap with its transpose
 ⁷{ for each input:

 ╵× repeat the canvas input+1 times horizontally
 ↔ reverse horizontally
 ¹ the input,
 A× times 10,
 ├ plus 2
 m mold the canvas to that width
 ↶ rotate the canvas anti-clockwise, setting up for the other input

JavaScript (ES8), 167 161 159 bytes

Takes input as (width)(height).

w=>h=>(g=h=>h?g(--h)+`
`+([4106,4016,31305,21504,17010]['0102344320'[h%=10]]+'').replace(/./g,c=>'\/'[c^h>5]||''.padEnd(c-1)).repeat(w+1).slice(8):'')(h*10+2)

Try it online!

How?

We encode the upper half of the pattern with digits:

• 
  $0$ means
  


• 
  $1$ means /
  


• 
  $n=2$ to $7$ means $n-1$ spaces

This gives:

0 ···/····· --> [3 spaces] [/] [] [5 spaces] --> 4106
1 ···/····· --> [3 spaces] [] [/] [5 spaces] --> 4016
0 ···/····· --> [3 spaces] [/] [] [5 spaces] --> 4106
2 ··/······ --> [2 spaces] [/] [2 spaces] [] [4 spaces] --> 31305
3 ·/······· --> [1 space] [/] [4 spaces] [] [3 spaces] --> 21504
4 /······/ --> [/] [6 spaces] [] [/] [] --> 17010

For the lower half, we use the rows $4,3,2,0$ with / and inverted.

Perl 5 -p, 148 bytes

$_='3A3'x$_.$/.'3B3
3A3
2/2\2
1/4\1
A6A
B6B
1\4/1
2\2/2
3B3
3A3
'=~s/^.*$/$&x$_/mger x<>.'3B3'x$_;s|A+|/\|g;s|B+|\/|g;s/d/$"x$&/ge;s|^ | |gm

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Haskell, 179 bytes

k '\'='/'
k '/'='\'
k x=x
f x=take(10*x+2)
w#h=map(f w.cycle).f h.drop 9.cycle$(++).reverse=<<map(map k)$["\/\ /"," \ / "," \ / "," \/ "," /\ "]

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Haskell, 181 bytes

k '\'='/'
k '/'='\'
k x=x
f x=take(10*x+2)
w#h=map(f w.cycle).f h.drop 9.cycle$(++).reverse=<<map(map k)$map t[49200,36058,31630,30010,29038]
t 0=""
t n="\ /"!!mod n 3:t(div n 3)

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Charcoal, 24 23 bytes

´/↘²‖Ｃ↘‖ＭLＦ⊖ＮＣχ⁰Ｆ⊖ＮＣ⁰χ

Try it online! Link is to verbose version of code. Explanation:

´/↘²

Draw one eighth of the original pattern.

‖Ｃ↘

Duplicate it to make one quarter of the original pattern.

‖ＭL

Duplicate it twice more to complete the original pattern.

Ｆ⊖ＮＣχ⁰

Copy the required number of times horizontally.

Ｆ⊖ＮＣ⁰χ

Copy the required number of times vertically.

Note: I think ‖Ｍ↘L should work for a two-byte saving but a) M↘ crashes and b) M↖ doesn't crash but appears to produce incorrect output.

JavaScript (ES6), 139 bytes

This is using quite a different approach from my initial answer, so I'm posting this separately.

Takes input as (width)(height).

w=>h=>(g=x=>y>8?` /\
`[a=(x+y*9)%10,b=(x+y)%10,x?(y%10>3&&2*(a==8)|b==5)|(y%10<6&&2*(a==6)|b==7):3]+g(x--?x:--y&&w):'')(w=w*10+2,y=-~h*10)

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