I've taught this lesson to grade 2, 3, 4, and 5 students (EFL) in Japan.
Draw a circle on the board, ask the class, "What picture is it?" <they won't get clock, but that's not the point really. Notice the structure you're introducing: What ____ is it?>
Draw a dot in the center of the circle, ask the class, "What picture is it?" <they won't get clock>
Draw both clock hands in the circle, ask the class, "What picture is it? <they should get clock, either in their first langauge (L1) or in English>
Draw two straps on each side of the clock, ask the class, "What picture is it?" <they might get watch>
Say to the class, watch this (put emphasis on the word "watch". Now, erase the straps, and ask the class, "What picture is it?" <they should get that it's a clock>
Now, draw the straps back in again and ask, "What picture is this?" <they should get watch> If not, do it again.
*Note, leave the pciture of the clock on the board.
Review Numbers 1-12
Write the numbers on the board in any order--it's important to make sure the numbers are not in order. Tell the students to put their heads down--no looking--then the teacher erases one of the numbers; have the students look up. The first student to call out the missing/erased number is the winner. *Note, when the students have their heads down, now and then write in numbers you had erased. *Note, pay special attention to 7, 9, 11, and 12.
Discovery: Activity #1
Beside the picture of the clock that you drew on the board, write in the number 1, and say "One", then write in this symbol : and say nothing, then write in O and say "Oh". You should have this on the board 1:OO, with the last O being the clock that you had drawn earlier. Say it aloud again: "One o'clock". Now, erase the number 1 and add in the number 3 or 7 or whatever, until the students get the structure X o'clock. Remember to ask the students, "What time is it?" as you change the numbers.
Erase the clock and fill in the missing slots with 5 or 10 or 15 or 20 and so on, if that is the students know numbers greater than 20. Say the structures aloud;e.g., 1:05 (one oh-five), 1:10 (one ten), and so on. Remember to ask the students, "What time is it?" as you change the numbers.
Practice: Activity #2
Play, What time is it, Mr Wolf?
Move the desks to the side of the room, have the students stand at the back, the teacher stands at the front of the room.
Explain the game: The students call out "What time is it, Mr Wolf? to which the Wolf calls out a time; e.g., It's 1 o'clock. The students take one step towards the wolf. Then the students call out again, "What time is it, Mr Wolf?", and the Wolf gives a time, and the students advance forward. When the students are close enough--within catching distance, the Wolf instead of calling out a time says, "It's lunch time!" and tags the nearest student. Game over, and the student who was caught now becomes the wolf and calls out the times.
Opportunity: Activity #3
On the board the teacher writes these times (just the numbers): the time you get up, the time you eat breakfast, the time you get to school, the time you eat lunch, the time you go home, the time you eat dinner, and the time you go to bed.
The students are placed in groups and given a simple grid card that looks like your daily schedule. In their groups they have to decide which times written on the board go where on the schedule in front of them. That is, they have to guess where the times fit in to your schedule. *Note, you can write "day" and "night" on the schedule with a sun and a moon, respectively, with lunch in the middle. **Note also, grade 2 students cannot do this activity. I had them draw a clock.
Once all the teams have completed the schedule, they, one by one, have to ask you, "What time do you_______?" If the answer you give matches the answer they wrote down on their grid, they win a point for their team.
Ask the students when they eat breakfast, what time they go to bed, and so on. That last question, about bedtime, will gain a great deal of attention from their classmates.
All the best, and I hope it goes well for you.