Method

Write all $26$ letters and $10$ numbers randomly in a $6 \times 6$ grid with columns and rows indexed by the word ADFGVX.

  A D F G V X
A N A 1 C 3 H
D 8 T B 2 0 M
F E 5 W R P D
G 4 F 6 G 7 I
V 9 J 0 K L Q
X S U V X Y Z

Then, for some plaintext, replace each letter with the $(row, column)$ index where it is placed. So

Plaintext: WAR
W -> FF
A -> AD
R -> FG

Ciphertext: FFADFG

Examples

.	A	D	F	G	V	X
A	2	1	J	U	N	E
D	1	7	8	D	C	M
F	B	R	T	V	W	X
G	A	F	3	G	H	4
V	I	5	K	L	6	O
X	P	Q	9	S	Y	Z
Let plaintext be `STARRY DYNAMO`. Then,

S -> XG
T -> FF
A -> GA
R -> FD
R -> FD
Y -> XV

D -> DG
Y -> XV
N -> AV
A -> GA
M -> DX
O -> VX

which is our ciphertext.